Anna Elisabeth Höhl Scientific Understanding

**Philosophy – Enlightenment – Critique** Volume 2

#### **Editorial**

The book series **Philosophy – Enlightenment – Critique** aims to promote philosophical thinking dedicated to a future worth living for everyone in times of global crisis. Climate change, political and religious authoritarianism, and growing social inequalities – the manifold and interconnected issues of our time require a return to the power of reason. In the spirit of a new enlightenment, the series initiates a dialog between different philosophical schools and traditions that critically scrutinize the past and present and explore the ramifications of sustainable alternatives. This requires a re-examination, re-interpretation and revision of the philosophical canon. The series also reveals the emancipatory potential inherent in the interplay between philosophy and other disciplines such as technology or aesthetics.

**Anna Elisabeth Höhl**, born in 1992,is a philosopher of science and works as a project coordinator at the Institute of Philosophy at Leibniz Universität Hannover. After degrees in physics, history and philosophy of science, she did her doctorate at Universität Bielefeld as a member of the DFG-funded Research Training Group "Integrating Ethics and Epistemology of Scientific Research". Her research focusses on topics in general philosophy of science and she approaches abstract questions through detailed analyses of concrete episodes from scientific practice.

Anna Elisabeth Höhl **Scientific Understanding**

What It Is and How It Is Achieved

This work was accepted as doctoral dissertation by the Faculty of History, Philosophy and Theology of Bielefeld University in 2022. Examiners: Prof. Dr. Marie I. Kaiser, Prof. Dr. Mathias Frisch

This research was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project 254954344/GRK2073.

This publication was funded by the Open Access Publishing Fund of the Leibniz Universität Hannnover and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Project 254954344/GRK2073.

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#### **First published in 2024 by transcript Verlag, Bielefeld © Anna Elisabeth Höhl**

Cover layout: Maria Arndt, Bielefeld Printed by: Majuskel Medienproduktion GmbH, Wetzlar https://doi.org/10.14361/9783839472620 Print-ISBN: 978-3-8376-7262-6 PDF-ISBN: 978-3-8394-7262-0 ISSN of series: 2941-8151 eISSN of series: 2941-816X

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# **Contents**

# **Acknowledgements**

This book is the result of a doctoral project I have been conducting for three and a half years. Such complex and long-term projects are never realized or completed by one individual alone without the support and advice from other people. I had the good fortune to have had many excellent and fantastic people accompanying me throughoutmy time as a PhD student. I would like to take this opportunity to express my gratitude.

To begin with, I would like to thank my first supervisor, Prof. Dr. Marie I. Kaiser, for her support and guidance over the whole period of my doctoral project. She helped me to find and follow my way, already at the very beginning of the project, and at every point in time where I had to make crucial decisions. I very much appreciated her criticism, which always challenged me to scrutinize my thoughts and intuitions. Many thanks go to my second supervisor, Prof. Dr. Mathias Frisch, as well. He brought the topic of scientific understanding to my attention in the first place and gave me valuable feedback especially towards the end of the project.

Also, the wider environment in which I conducted my doctoral project contributed significantly to its successful completion. In particular, I would like to thank all the members of the Research Training Group 2073 in Bielefeld as well as in Hannover. Furthermore, I am grateful to the members of the Philosophy Department at Bielefeld University for creating and maintaining such a warm and friendly working atmosphere. Notably, my gratitude goes to all the members of the PhilBio Team and the PoS Seminar for reading and commenting on drafts of my work throughout the years. Additionally, I would like to thank Marcus Bachmann, Daphne Broeks, Linda Holland, Henk de Regt, Stefan Sleeuw and Javier Suárez for inspiring and in-depth discussion about the various dimensions and aspects of understanding.

Especially, my gratitude goes to Minea Gartzlaff, Ina Gawel, Saana Jukola, Milla Lifke, Rui Só Maia, Basel Myhub, Rose Trappes and Roel Visser for their assistance and friendship over the years. All of you made the time as a doctoral student much more enjoyable and an invaluable experience.

Finally, I would like to thank my family, without whose continuous support over the years I would not have made it to where I am now.

# **List of Figures**

# **1. Introduction**

Human beings strive to understand the world they inhabit. Aiming and attempting to understand something is ubiquitous in our everyday lives. Every human has witnessed situations in which, for example, a child wants to understand why one has to pay money when buying groceries from the supermarket, why someone is sad, or why her parents stay awake longer in the evening while she has to go to bed already. The same is of course also true of adults, although they may want to understand different things than children. Adult humans want to understand why a colleague is in a very bad mood, why there was a financial crisis, or how it was possible that populist parties gained more and more influence. And scientists strive to understand phenomena in the natural or social domains they are researching. Understanding phenomena is viewed to be one aim of science, as scientists occasionally state themselves. In biology, for instance, "a model organism [that] is a non-human species is extensively studied to *understand* specific biological phenomena."1

Despite the pervasive presence of instances and attempts of human beings to understand something in the world, the concept of *understanding*, what understanding is and how it is actually achieved, is hard to explicate. The uncertainty and confusion concerning the concrete meaning of *understanding* is not bound to a specific domain. From personal conversations with educators, I know that one goal of educational science is to develop tools or methods to determine whether pupils have understood what they are supposed to learn and understand in school. However, educators do this without having any clear concept or notion of *understanding*. They want to be able to measure something of which they have no idea what it actually is.2 The controversial nature of understanding also becomes apparent in such provoca-

1 Sakaguchi, K. et. al. (2019), "Comprehensive Experimental System for a Promising Model Organism Candidate for Marine Teleosts." *Scientific Reports*, 9 (4948), DOI: 10.1038/s41598-019-4 1468-8, my emphasis.

2 This is the personal assessment of a friend of mine working in education science. Other educators might have a different opinion on that matter. However, if a fixed conception of understanding were employed in education science, my friend probably would not have a problem with it.

tive claims as "I think I can safely say that nobody understands quantum mechanics"3 famously posed by Richard Feynman.

This book is a contribution to the philosophical research on (scientific) understanding. Surprisingly, philosophy has not paid much attention to understanding throughoutits history,although understanding seems to be an ubiquitous epistemic activity as well as an unclear and contested concept. A philosophical interest in understanding emerged only quite recently within the last 25 years. Why has understanding been neglected by philosophers for such a long time and why has it attracted attention in recent times?

## **1.1 Tracing understanding through the history of philosophy**

Understanding was already a topic of interest in ancient philosophy. In fact,it is proposed by some contemporary scholars that the more appropriate translation for the ancient Greek word *epistēmē* may be understanding, and not knowledge. For example, Julia Annas argues that in Plato's view, a person who has *epistēmē* does not merely possess various truths, but rather a systematic understanding of things.4 Jonathan Lear makes a similar claim for Aristotle, namely that "to have *epistēmē* one must not only know a thing, one must also grasp its cause or explanation. This is to understand it: to know in a deep sense what it is and how it has come to be."5 These interpretations of *epistēmē* reflect, according to Stephen Grimm, the currently widely accepted view that knowledge is quite easy to gain, while it seems harder to achieve understanding.6 For example, I can know that I have blond hair just by looking at it, but understanding why I have blond hair or how I came to have blond hair demands something in addition. A reason for this difference might be that pieces of knowledge can be isolated or atomistic, at least in principle. I can know that I have blond hair without knowing anything else about, for example, genetics, inheritance, and the hair colors of my parents and ancestors. By contrast, targets of understanding seem to be more structured and interconnected. Although this might be due to the complex nature of targets that we want to understand, like the Second World War or the evolution of species, a certain degree of interconnectedness is also present in the understanding of isolated events. Understanding why a glass shatters requires connecting it with other events, for example the bumping of my elbow. Admittedly,

3 Feynman, R. P. (2017 [1965]), *The Character of Physical Law*. Cambridge (MA), MIT Press, p. 129.

4 See Annas, J. (1981), *An Introduction to Plato's Republic*. Oxford, Clarendon Press, chapter 10.

5 Lear, J. (1988), *Aristotle: The Desire to Understand*. New York, Cambridge University Press, DOI: 10.1017/CBO9780511570612.002, p. 6.

6 See Grimm, S., "Understanding", *The Stanford Encyclopedia of Philosophy* (Summer 2021 Edition), Edward N. Zalta (ed.), forthcoming URL = https://plato.stanford.edu/archives/sum20 21/entries/understanding/ (last accessed April 11th, 2022), section 1.1.

the Greek philosophers seem to have held a very demanding concept of understanding that exceeds such mundane cases of understanding, as the understanding of the shattering of a glass, by far. Nevertheless,*epistēmē* is more similar to our contemporary notion of *understanding* than to the contemporary concept of *knowledge*, due to its emphasis on systematicity and interconnectedness.7

So, *understanding* is by no means a new concept in philosophy. Still, it has very much disappeared from the philosophical stage, and epistemologists focused instead on propositional knowledge. Why did that happen? No one really knows. Grimm presents two hypotheses. Perhaps the shift from understanding to knowledge was a reaction to the rise of skepticism in Hellenistic philosophy.8 Alternatively or additionally, the wars of religion in 16th and 17th century Europe necessitated a focus on knowledge, as it became important to differentiate between good and bad knowledge claims.9 Despite these first attempts at explaining the lack of understanding in the field of philosophy, the disappearance of understanding from philosophical debates is an unexplored issue so far, and I hope that research in history of philosophy will shed more light on it in the future.

It was not until the 19th century that the notion of understanding gained attention again in philosophy. Johann Gustav Droysen and Wilhelm Dilthey (re-)introduced understanding together with the *Verstehen-Erklären* dichotomy. It was their goal to elucidate the difference between the humanities (*Geisteswissenschaften*) and the natural sciences (*Naturwissenschaften*), and the *Verstehen-Erklären* dichotomy was taken to fulfill this purpose. For Droysen and Dilthey, understanding is the goal of the humanities, as the humanities are concerned with the intentions of (historical) actors and the interpretation of artefacts like texts or works of art. Therefore, understanding is subjective, according to Droysen and Dilthey. The natural sciences, in contrast, aim at uncovering the causes and general laws that are the basis of observed natural phenomena. Finding explanations of natural phenomena was, for Droysen and Dilthey, a purely objective endeavor.10 Both scholars aimed at constituting an adequate theoretical as well as methodological basis for the "human sci-

7 See ibid.

8 See Zagzebski, L. (2001), "Recovering Understanding." In Steup, M. (ed.), *Knowledge, Truth, and Duty: Essays on Epistemic Justification, Responsibility, and Virtue*, pp. 235–252, New York, Oxford University Press, DOI: 10.1093/0195128923.003.0015.

9 For a systematic reconstruction of the history of epistemology, see Pasnau, R. (2017), *After Certainty: A History of Our Epistemic Ideals and Illusions*. New York, Oxford University Press, DOI: 10.1093/oso/9780198801788.001.0001.

10 See Beiser, F. C. (2011), *The German Historicist Tradition*. New York, Oxford University Press, DOI: 10.1093/acprof:oso/9780199691555.001.0001, chapter seven and eight; and Makkreel, R., "Wilhelm Dilthey", *The Stanford Encyclopedia of Philosophy* (Spring 2021 Edition), Edward N. Zalta (ed.), URL = https://plato.stanford.edu/archives/spr2021/entries/dilthey/ (last accessed April 11th, 2022).

ences", covering the humanities, to establish them as distinct from, but equally "scientific" as the natural sciences.11 The *Verstehen-Erklären* dichotomy had a strong and complex influence on the Vienna Circle, and therefore on logical empiricism in general, and would maintain a long lasting impact on the philosophy of science.12 However, apart from its prominent status in the debate about the *Verstehen-Erklären* dichotomy in the 19th century, understanding has never been seen as or taken to be an interesting or important topic for philosophers since antiquity. No one really cared about understanding.

## **1.2 The neglect and (re-) discovery of understanding …**

Given the absence of the notion of understanding from philosophical controversies for millennia, why has it become a topic for philosophy within the last few decades? Why do philosophers nowadays care about understanding? Baumberger, Beisbart & Brun identify three reasons for this trend:

Understanding seems to be a central good that we try to realize when we think about the world. More specifically, the value of understanding seems to surpass that of knowledge. We can know something without understanding it. […] The second reason for devoting attention to understanding is that understanding is a central goal of science. String theorist Greene goes so far as to characterize science in terms of understanding: "Science is the process that takes us from confusion to understanding in a manner that's precise, predictive and reliable." […] The third reason to look at understanding derives from developments within epistemology.13

11 See for example Meinefeld, W. (1995), *Realität und Konstruktion. Erkenntnistheoretische Grundlagen einer Methodologie der empirischen Sozialforschung*, Wiesbaden, VS Verlag für Sozialwissenschaften, pp. 31–35, DOI: 10.1007/978-3-663-11243-3.

12 For more details on this relation, see for example Apel, K.-O. (1982), "The Erklären-Verstehen controversy in the philosophy of the natural and human sciences." In Fløistad, G. (ed.), *La philosophie contemporaine / Contemporary philosophy*, International Institute of Philosophy / Institut International de Philosophie, vol 2, pp. 19–49, Dordrecht, Springer, DOI: 10.1007/978- 94-010-9940-0\_2; or Uebel, T. (2010), "Opposition to *Verstehen* in Orthodox Logical Empiricism." In Feest, U. (ed.),*Historical Perspectives on Erklären and Verstehen*, pp. 291–309, Dordrecht, Springer, DOI: 10.1007/978-90-481-3540-0\_15.

13 Baumberger, C., Beisbart, C. & Brun, G. (2017), "What is Understanding? An Overview of Recent Debates in Epistemology and Philosophy of Science." In Grimm, S., Baumberger C. & Ammon, S. (eds.), *Explaining Understanding. New Perspectives from Epistemology and Philosophy of Science*, pp. 1–34, New York and London, Routledge, pp. 2f; and Greene, B. (2008), "Put a Little Science in Your Life." New York Times, Open Ed., June 1, https://www.nytimes.com/200 8/06/01/opinion/01greene.html (last accessed October 3rd, 2023).

Concerning the third reasons, the authors are referring to arising difficulties for and criticisms of justification conditions in accounts of knowledge. As these three reasons indicate, the two philosophical disciplines that are primarily concerned with understanding these days are philosophy of science and epistemology. Let us take a closer look at why understanding has not been worthy of inquiry for these disciplines for a long time, and why and how that changed.

## 1.2.1 … in philosophy of science

The impact from the *Verstehen-Erklären* dichotomy, in which understanding was viewed as something subjective while explanation as something objective, became most apparent and was even amplified through the work of Carl Gustav Hempel in the 1960s. Due to his influential work, the notion of understanding was actively downplayed in philosophy of science for a long time. Essentially, Hempel was worried that understanding would be a threat to the objectivity of science. In Hempel's days, understanding was viewed as a subjective and psychological concept that – although it cannot be eliminated from science as science is conducted by human beings – should not be taken as a constitutive component of science. Explanation, on the contrary, is essential for science in Hempel's view. In a nutshell, the mere fact that some individual scientist does not understand some explanation of a phenomenon says nothing at all about the objectivity of the explanation. A good and objective scientific explanation of a phenomenon should be correct independently of any specific audience or context. As Hempel himself puts it:

For scientific research seeks to account for empirical phenomena by means of laws and theories which are objective in the sense that their empirical implications and their evidential support are independent of what particular individuals happen to test or to apply them; and the explanations, as well as the predictions, based upon such laws and theories are meant to be objective in an analogous sense. This ideal intent suggests the problem of constructing a non-pragmatic concept of scientific explanation.14

Only few philosophers offered resistance to Hempel's subjectivist view of understanding, but there were some. As early as 1974, Michael Friedman argued that just because understanding seems to have some psychological element,it does not follow that understanding is purely subjective, uninteresting or unimportant for philosophers of science.15 Eventually, knowledge has a psychological element, too, because

14 Hempel, C. G. (1965), *Aspects of Scientific Explanation and Other Essays in the Philosophy of Science*. New York, Free Press, p. 426.

15 See Friedman, M. (1974), "Explanation and Scientific Understanding." *Journal of Philosophy*, 71 (1), pp. 5–19, DOI: 10.2307/2024924.

of the belief condition, but this does not amount to a degradation of knowledge as being purely or mainly subjective. And Jaegwon Kim pointed out that humans aim at explaining things because we want to understand them. Hence, in Kim's view, it is a grave mistake to separate accounts of explanation from understanding.16

However, proponents of understanding could not remove the reservations about this notion in philosophy of science for a significant period of time. Even in the early 2000s, suspicions concerning understanding were actively endorsed, for example by John Trout, who defended the Hempelian objectivist account of explanation as well as his subjectivist view of understanding. According to Trout, understanding merely is a *Eureka!* or *Aha!* feeling, a product of types of biases known in cognitive psychology: "This sense of understanding alone is not necessarily a reliable guide to truth, nor is it a necessary condition for good explanation. Still less is it sufficient for good explanation."17 A significant change of this situation was only brought about by the distinction between the "feeling" or phenomenology of understanding and genuine understanding introduced by Henk de Regt.18 He also extensively engaged with Hempel's work in order to argue that understanding should not be taken as purely subjective and pragmatic. De Regt should be successful. By now, understanding is receiving more and more attention within philosophy of science, it is viewed as a legitimate and interesting topic for philosophers of science, and de Regt can be seen as the most important founding father of the contemporary debate on understanding in this discipline.

While understanding is a respected topic within philosophy of science by now, specific questions or issues concerning understanding receive special attention. According to Grimm, philosophers of science are particularly interested in the relation of understanding and explanation, as well as the relation of understanding and idealization, where the notion of idealization is intended to cover idealized models and representations.19 Concerning the first issue, "the relationship between explanation and understanding remains controversial."20 Grimm differentiates between two main approaches to this topic, which are the "understanding-first" approach versus the "explanation-first" approach. The "understanding-first" approach takes understanding to be "conceptually prior to, or more basic then, the notion of expla-

16 See Kim, J. (1994 [2010]), "Explanatory Knowledge and Metaphysical Dependence." *Philosophical Issues*, 5, pp. 51–69, Reprinted in Kim, J. (2010), *Essays in the Metaphysics of Mind*. New York, Oxford University Press, DOI: 10.1093/acprof:oso/9780199585878.001.0001.

17 Trout, J. D. (2002), "Scientific Explanation And The Sense Of Understanding." *Philosophy of Science*, 69 (2), pp. 212–233, DOI: 10.1086/341050, p. 213.

18 See de Regt, H. W. (2004), "Discussion Note: Making Sense of Understanding." *Philosophy of Science*, 71 (1), pp. 98–109, DOI: 10.1086/381415.

19 See Grimm (2021), section 4.

20 Ibid.

nation."21 That is, explanation serves the end of understanding, and the goodness or "explanatoriness" of any explanation is assessed in terms of its capacity to generate understanding. Proponents of the "understanding-first" approach include Daniel Wilkenfeld, Paul Humphreys, and Angela Potochnik, among others.22 By contrast, according to the "explanation-first" approach, most prominently endorsed by Kareem Khalifa, the discussion of understanding is nothing but a repacking of existing theories of explanation:

All one needs for a plausible account of understanding is a plausible account of what counts as a good or correct explanation, combined with a plausible account of knowledge. Understanding therefore amounts to *knowing a correct explanation*. But then nothing new or special is needed to theorize about understanding; our accounts of explanation and our theories of knowledge do all the important theoretical work.23

Intuitions regarding these two approaches vary significantly, as the basic issue concerns the question of whether or not understanding *why p* does in some way exceed knowing *why p*.

The second interesting issue for philosophers of science, according to Grimm, is the relation of understanding and idealizations. Like explanation, idealization is a long-standing central and established topic in philosophy of science. Explanation as well as idealization are ubiquitous in science. The central challenge posed by idealization is to account for their capacity to provide real epistemic benefits without adhering to the truth (at least not in a strict or straightforward sense). All idealizations misrepresent or falsify the worldin some way, e.g. by appealing to fully rational agents or frictionless planes, or through omitting certain factors, e.g. long range intermolecular forces.24

Yet if idealizations provide epistemic benefits, and we cannot readily think of the benefits in terms of truth, then how exactly should we think about them? According to some philosophers, we should think not in terms of truth but rather in terms

21 Ibid.

22 For more details, see e.g. Wilkenfeld, D. A. (2013), "Understanding as Representation Manipulability." *Synthese*, 190 (6), pp. 997–1016, DOI: 10.1007/s11229-011-0055-x; and Humphreys, P. (2000), "Analytic Versus Synthetic Understanding." In Fetzer, J. (ed.), *Science, Explanation, and Rationality: The Philosophy of Carl G. Hempel*, pp. 267–286, Oxford, Oxford University Press, DOI: 10.1093/oso/9780199334872.003.0017; and Potochnik, A. (2017), *Idealization and the Aims of Science*. Chicago (IL), University of Chicago Press, DOI: 10.7208/9780226507194.

23 Grimm (2021), section 4.1; see especially Khalifa, K. (2017b), *Understanding, Explanation, and Scientific Knowledge*. Cambridge, Cambridge University Press, DOI: 10.1017/9781108164276.

24 See Grimm (2021).

of understanding. Understanding is the epistemic benefit we receive from idealizations, and understanding and truth can come apart. On this view, understanding (unlike knowledge) can therefore be "non-factive".25

Concerning the details of how exactly idealizations might provide understanding, different accounts have been offered, for example by Angela Potochnik, Catherine Elgin, and Michael Strevens.26 Furthermore, there is no general consensus that understanding can be non-factive. To put it differently, it is highly contested whether a representation that does not (somehow) answer to the facts can enable (genuine) understanding.27

Thus, the core topics surrounding understanding (although not the only ones) that philosophers of science are interested in relate to two traditional, central issues within the field, explanation and idealization. However, the second philosophical discipline that has also (re-)discovered understanding as a topic of interest is epistemology. Why did epistemologists become interested in understanding?

#### 1.2.2 … and in epistemology

In epistemology, the notion of understanding has not been actively devalued as in the philosophy of science, but rather neglected or ignored, according to Grimm.28 As stated in section 1.1, the reasons for this disinterest in understanding throughout the history of western philosophy are not really known, but it is possible to identify reasons why this situation changed,i.e. why epistemologists started to be interested in understanding towards the end of the 20th century (again). Grimm identifies three reasons for this development.These three reasons are in line with, though not identical to, the reasons that Baumberger, Beisbart & Brun present for this trend, mentioned in section 1.2.

The first observation by Grimm is that, as especially Elgin argued, some of the greatest intellectual achievements of humanity, which can be found, for instance, in the sciences and arts, are actually not targeted at what epistemologists traditionally view as knowledge, but rather at something that is more plausibly conceptualized as

25 Ibid, section 4.2.

26 See Potochnik (2017), Elgin, C. Z. (2017), *True Enough*. Cambridge (MA), MIT Press; and Strevens, M. (2017), "How Idealizations Provide Understanding." In Grimm, S., Baumberger C. & Ammon, S. (eds.), *Explaining Understanding. New Perspectives from Epistemology and Philosophy of Science*, pp. 37–49, New York and London, Routledge.

27 For an overview of different positions and arguments in favor of and against (moderate) factivity and non-factivity, see Baumberger, Beisbart, & Brun (2017).

28 See Grimm (2021), section 1.2.

understanding.29 Second, he argues that the interest in understanding was driven by virtue epistemologists. For example, Linda Zagzebski maintained that the focus of epistemology on knowledge as one epistemic good is too narrow, as it does not do justice to other highly valued epistemic goods like e.g. wisdom or understanding.30 And third, Jonathan Kvanvig influentially argued that understanding is distinctively valuable, while knowledge is not.31 Grimm concludes that all the different lines of arguments accused the field of epistemology of having a too narrow and one-sided focus on knowledge and that "epistemology needed to be broadened so that goods such as understanding could be given their proper due, and their claims resonated with other epistemologists."32

The first observation presented by Grimm supports the second reason for the new interest in understanding presented by Baumberger, Beisbart & Brun, namely that understanding is a central goal of the sciences (and potentially also of other areas of human action). Grimm's second and third observation concerning the views from (virtue) epistemology resembles the first reason provided by Baumberger, Beisbart & Brun, which is the (potential) special epistemic value of understanding. Whatever understanding is, it seems to be something that goes over and above knowledge (and the same could be argued for wisdom, for example). If this is the case, then understanding is epistemically more valuable than knowledge, and the traditional focus on knowledge in epistemology becomes questionable.

[In this context, it has been noted several times that] knowledge may easily be acquired through the testimony of experts; understanding, by contrast, seems more demanding and requires that an epistemic agent herself puts together several pieces of information, grasps connections, can reason about causes, and this too suggests an added value. […] The problem of accounting for a supposed special value of knowledge is now called *the value problem for knowledge*. Epistemology escapes this problem if it turns to understanding.33

29 See particularly Elgin, C. Z. (1991), "Understanding: Art and Science." *Midwest Studies in Philosophy*, 16, pp. 196–208, DOI: 10.1111/j.1475-4975.1991.tb00239.x. For a more recent elaboration of her ideas concerning understanding, see Elgin (2017).

30 See Zagzebski, L. (1996), *Virtues of the Mind. An Inquiry into the Nature of Virtue and the Ethical Foundations of Knowledge,* New York, Cambridge University Press, DOI: 10.1017/ CBO9781139174763; and Zagzebski (2001).

31 See Kvanvig, J. L. (2003), *The Value of Knowledge and the Pursuit of Understanding*. New York, Cambridge University Press, DOI: 10.1017/CBO9780511498909.

32 Grimm (2021), section 1.2.

33 Baumberger, Beisbart & Brun (2017), p. 3, original emphasis. For a detailed discussion of *the value problem for knowledge*, see Pritchard, D., Millar, A. & Haddock, A. (2010), *The Nature and Value of Knowledge: Three Investigations*, Oxford, Oxford University Press, DOI: 10.1093/acprof:oso/9780199586264.001.0001. Jonathan Kvanvig also explicity advocates the special value of understanding in comparison to knowledge, see for example Kvanvig (2003).

However, and quite unsurprisingly, the alleged special epistemic value of understanding is not universally accepted and objections are put forward.34

Investigations on and discussions about the possible special epistemic value of understanding are related and intertwined with the third reason that Baumberger, Beisbart & Brun identify for the interest in understanding, namely other developments within epistemology that concern the notion of justification. Apparently, strong intuitions persist that a justification for a belief, which would turn the belief into knowledge, is on the one hand accessible for the epistemic agent, is internal to her, and on the other hand that the belief is justified through being embedded in a coherent web of beliefs.These views on justification for beliefs are called internalism and coherentism.35

[Baumberger, Beisbart & Brun observe that while] intuitions supporting internalism and coherentism seem deep-seated, it has been proven difficult to save them in an account of knowledge. Internalism about epistemic justification is threatened by a regress problem. Coherentists have a hard time to show how coherence is related to truth, which is supposed to be the aim of belief and a central feature of knowledge. However, an immediate access to the reasons for a belief and the ability to connect a belief with others seem to be central for understanding.36

Hence, they conclude that internalist and coherentist intuitions can appropriately account for understanding, while they are (or might be) inapplicable to knowledge. Again, such views that allocate internalist or coherentist intuitions to understanding, and additionally intuitions from virtue epistemology, are contested as well.37

34 See for instance Carter, J. & Gordon, E. (2014), "Objectual Understanding and the Value Problem." *American Philosophical Quarterly*, 51 (1), pp. 1–13; or Khalifa (2017b), chapter 8.

35 See for example Pappas, G., "Internalist vs. Externalist Conceptions of Epistemic Justification", *The Stanford Encyclopedia of Philosophy* (Fall 2017 Edition), Edward N. Zalta (ed.), URL = https: //plato.stanford.edu/archives/fall2017/entries/justep-intext/ (last accessed April 11th, 2022); and Olsson, E., "Coherentist Theories of Epistemic Justification", *The Stanford Encyclopedia of Philosophy* (Fall 2021 Edition), Edward N. Zalta (ed.), URL = https://plato.stanford.edu/archiv es/fall2021/entries/justep-coherence/ (last accessed April 11th, 2022).

36 Baumberger, Beisbart & Brun (2017) pp. 3f.

37 See for instance Grimm, S. (2017), "Understanding and Transparency." In Grimm, S., Baumberger C. & Ammon, S. (eds.), *Explaining Understanding. New Perspectives from Epistemology and Philosophy of Science* pp. 212–229, New York and London, Routledge; and Khalifa, K. (2017a), "Must Understanding be Coherent?" In Grimm, S., Baumberger, C. & Ammon, S. (eds.)*, Explaining Understanding.New Perspectivesfrom Epistemology and Philosophy of Science*, pp. 139–164, New York and London, Routledge.

#### 1.2.3 The current state of play

Where does all this leave us? In sum, various reasons have led to the recent interest of philosophers in understanding.Most fundamentally,it has been acknowledged that understanding is a central epistemic good that humans try to and want to achieve, in science as well as elsewhere. Because of the recognition of this central value of understanding, philosophers of science and epistemologists began paying attention to the concept. The engagement with understanding has opened up new possibilities to solve already known problems and answer open questions in the respective disciplines. For philosophy of science, the examination of understanding enables analyses of a crucial (or potentially the most important) scientific aim and the function of idealizations in scientific research, among others. In epistemology, the work on understanding offers solutions to central issues in the field, such as *the value problem for knowledge*, or problems concerning different accounts of epistemic justification.

Furthermore, the topic of understanding has yielded an extensive exchange between these two philosophical disciplines, which is a rare phenomenon. Philosophers of science and epistemologists engage with and criticize each other's work in this area.This interdisciplinary research on the topic of understanding has resulted in a fruitful dialogue between the two philosophical disciplines, each of which contributes their own main interests, questions, and respective methods. Philosophy of science is interested in the understanding that scientists achieve of the phenomena they are researching or of the theories that they use, how scientists achieve this understanding, and how scientific understanding relates to other core concepts in science, such as theories, explanations, and models, among others. Epistemology, in contrast, is interested in the understanding that (human or rational) agents generally can gain.

Despite their differences, philosophers of science and epistemologists share the common ground in that the concept of understanding should be analyzed and provide each other with important insights. On the one hand, epistemologists (usually) take scientific understanding to be a special or in some sense distinctively valuable type of understanding,and hence they areinterestedin what philosophers of science have to say about it. On the other hand, any general inquiry into understanding in epistemology might reveal important insights for philosophers of science.

This dialogue between the two philosophical disciplines amounts to ever new research questions on understanding, including the following:

This list is not meant to be exhaustive, it shall just exemplify the diversity and amount of questions concerning understanding which puzzle philosophers.38 This book is a contribution to this thriving and new 'hot' topic and debate in philosophy.

## **1.3 Outline of this book**

The goal of this book is to provide a philosophical account of scientific understanding.That is, I develop and defend necessary and sufficient conditions for the understanding that scientists achieve of the phenomena they are studying through their research. To put it differently, I provide answers to these two main questions:

My starting point is the existing philosophical debate on understanding, including work on scientific understanding in particular, as well as on understanding in general. As I have stressed throughout the previous section, understanding is a topic of interest for philosophers of science as well as for epistemologists for the last three decades. Hence, perspectives and insights from both disciplines need to be consideredin any analysis on understanding.Chapters two, three and four cover, therefore, abstract and normative philosophical discussions and positions concerning characteristics of understanding and related concepts, such as explanation and ability or knowing-how.The philosophical literature already has a lot to offer for clarifying the notion of understanding, and I could only scratch the surface of the variety of topics and issues around understanding that are addressed in philosophy by now in the previous section.

Engaging with different and opposing views and arguments allows for the identification of core topics concerning understanding, together with underlying assumptions or intuitions regarding certain issues. A thorough examination of the existing philosophical literature on understanding provides an important navigation through the debate. It enables structuring the debate into more or less controversial or important topics with regard to specific questions, together with the genesis of certain camps within the debate, the arguments developed by proponents of

38 Further summaries of the philosophical debate on understanding and the questions that occupy philosophers are provided by Baumberger, Beisbart & Brun (2017) and Grimm (2021).

different views, and also the intuitions that are uphold within and across different camps. Taking already developed philosophical arguments and theories about aspects of understanding enables me to clarify my intuitions concerning understanding, why I agree with some scholars and not with others, and developing my own normative position on questions such as why scientific understanding should require explanation or why understanding should be conceptualized as an ability.

However, while abstract philosophical theorizing and argumentation is of course important, it is not sufficient for generating a meaningful account of scientific understanding. I am a philosopher of science and, hence, have acquired the specific methods and practices of my discipline. Since the Practice Turn in 1980s, through which philosophical as well as historical and social studies of science paid much more attention to the social, psychological, and material dimensions of scientific research, philosophy of science is (often) characterized by in-depth and detailed case studies or episodes from past or present scientific practice. I adhere to this practice, as it is my deepest conviction that philosophy has to take scientific practice seriously if it wants to generate and contribute any relevant or important insights about science.39 The most consistent and intuitive philosophical theory or argument will be meaningless if it cannot capture real and actual science.

Thus, while I draw on shorter examples from scientific as well as none-scientific contexts throughout my abstract philosophical discussions to support my claims, these examples cannot replace in-depth analyses of research episodes. Examples serve the purpose of illustrating or supporting claims or arguments. Analyses of research episodes shall, additionally, provide novel insights into the topic of interest, scientific understanding in this case. Hence, an analysis of an episode from scientific practice will follow my abstract philosophical discussions. Thereby, I can reassess the plausibility of my claims developed before, and also highlight novel insights about how scientists gain understanding that philosophical theorizing cannot deliver on its own. Taken together, the insights from my detailed engagement with the abstract philosophical debate and from the analysis of the concrete research episode allow me to generate a novel account of scientific understanding that will be meaningful for science in general.

Let me be more specific about the structure of this book. While insights from philosophy of science as well as epistemology need to be taken into account in any

39 For more information about the engagement of philosophy of science with scientific practice, see e.g. Soler, L., Zwart, S., Lynch, M. & Israël-Jost, V. (eds.) (2014), *Science After the Practice Turn in the Philosophy, History, and Social Studies of Science*. Studies in the Philosophy of Science 14, New York and London, Routledge. For insights into the relation between history and philosophy of science in particular, see Schmaltz, T. & Mauskopf, S. (eds.) (2012), *Integrating History and Philosophy of Science: Problems and Prospects*. Dordrecht, Springer, DOI: 10.1007/978- 94-007-1745-9.

analysis on understanding, this does not prohibit placing an emphasis on one of the respective disciplines. Again, I am a philosopher of science by training and approach the topic from the corresponding perspective. Thus, I start by introducing already existing accounts of scientific understanding put forward by the three philosophers of science Henk de Regt, Kareem Khalifa and Finnur Dellsén in chapter two. Presenting their accounts provides the basis for my analysis and allows for identifying central issues, question, and also shared assumptions related to scientific understanding. I restrict myself to the accounts of scientific understanding developed by philosophers of science in chapter two because this book focusses on scientific understanding. While I hope that my work will also be of value for epistemologists, I do not aim at providing an account of understanding in general. Hence, while I give epistemology its earned space throughout this book, especially in chapters three and four, I do not introduce any epistemological account of understanding at the beginning of my investigations in chapter two. Instead, I highlight the agreements and disagreements among de Regt, Khalifa, and Dellsén concerning scientific understanding and argue that two questions are especially striking:

These two questions provide partial answers to one of the main questions of this book, namely what scientific understanding is.The answer to the second main question, how scientists can or do achieve understanding, depends, in turn, on what scientific understandingis. In order to clarify what scientific understandingis and how scientists achieve it, which is the ultimate goal of this book, I first need to figure out whether understanding requires explanation and whether it is an ability or a type of knowledge. Thus, this book is structured as follows:

Having provided a starting point in chapter two, chapter three turns towards the question of whether scientific understanding requires explanation or not, a core question for philosophers of science, as I have indicated in section 1.2.1. Answering this question is not possible without clarifying what I mean by explanation. A clarification of the notion of explanation will be the first step to take in this chapter. Following that, I engage with several arguments and examples put forward to defend a separation or possible independence of understanding from explanation and challenge their plausibility for scientific understandingin particular.One line of thought is that understanding and explanation can fall apart, as the former is something tacit, while the latter is something explicit. Is it really that simple, is this straightforwardly the case? Furthermore, the philosophical literature on understanding intensively engaged with two types of understand so far: explanatory and objectual understanding. Explanatory understanding is viewed to require explanation. Objectual understanding, in contrast, is either independent of explanation or exceeds

explanatory understanding in some sense. How exactly do different scholars distinguish between these two types of understanding? And do the proposed distinctions really show a difference between two kinds of understanding, or do the differences merely point towards a difference in the degree of understanding? In other words, can objectual understanding be conceptualized as being independent of explanation? And finally, in light of the discussions conducted in this chapter, does it make sense to view scientific understanding as being possibly independent of explanation?

Chapter four addresses the question of whether understanding is an ability or a type of (propositional) knowledge. This chapter will probably be especially interesting for epistemologists, as it touches on central issues discussed in this field mentioned in section 1.2.2, including the demand for broadening epistemology's focus to other intellectual achievements than knowledge. Similarly to my approach in chapter three, I first need to clarify what I mean by ability. I will do that based on a broad literature survey covering work on abilities or knowing-how from philosophy of science, (virtue) epistemology, and metaphysics. Having generated a conceptualization of ability, the follow up question will be whether understanding should be viewed as an ability, or rather as a type of (propositional) knowledge. Can the notion of understanding and potential characteristics that are often intuitively ascribed to understanding be better accommodated by conceptualizing understanding as an ability, and not as a type of (propositional) knowledge? And if the answer to this question is affirmative, if understanding is taken to be an ability, how could understanding be manifested? In contrast to chapter three, where I mainly use and engage with the philosophical literature on understanding, my analysis in chapter four will be broader. Answering the questions of what abilities are, whether understanding should be conceived as an ability and if so, how understanding is manifested, requires a wider perspective that includes but also exceeds the debate on understanding, as more general questions concerning the nature of (propositional) knowledge and abilities need to be taken into account and then applied to discussions on understanding.

Chapter five then presents a change of perspective and differs significantly from the previous chapters, as it deals with an episode from scientific practice and the question how exactly scientists involved in this episode gained scientific understanding. The research episode covers the introduction of zebrafish as a new model organism into biological research through which biologists wanted to understand the genetic regulation of vertebrate development. A careful and detailed description of this research episode will, on the one hand, allow for testing whether the insights gained through abstract philosophical argumentation in chapters three and four have any meaningful implications for reals world science. On the other hand, analyzing the episode might allow for an identification of features of understanding that cannot be obtained by pure philosophizing detached from any realworld cases. What do real scientists need in order to understand a phenomenon they are researching? How do they actually achieve understanding? How do they proceed? Which steps do they undertake? This chapter aims at providing answers to these questions.

Finally, in chapter six, I bring all the different lines of thought developed in the previous chapters together and present my account of scientific understanding.This account will be an answer to the main questions of what scientific understanding is and how scientists achieve it, and will go beyond the concrete episode discussed in the previous chapter. Of course, the episode from biology serves an important purpose, but one cannot straightforwardly generalize from that episode to science as a whole, given the variety of different scientific disciplines. That is, the concrete insights from chapter five need to be abstracted in order to be relevant for scientific understanding, generally speaking, and these abstracted insights still need to be connected to the results from chapters three and four. How are understanding and explanation related? How do understanding, knowledge, and abilities tie in together? What do scientists need in order to understand a phenomenon? Which roles do the respective context and the research community in which any particular scientists is embedded play for understanding? In short, I will explain what I take scientific understanding to be and how scientists achieve it. To make my account of scientific understanding even more appealing, I will come back to the accounts by Henk de Regt, Kareem Khalifa and Finnur Dellsén introduced in chapter two, and I will emphasize the benefits of my account in comparison to their alternatives. Ultimately, chapter seven will provide a summary of the findings of this book and an outlook by pointing towards further questions and issues concerning scientific understanding that lie beyond the scope of this book.

In short, this book can be divided, roughly,into two parts. In chapters two, three, and four, I provide a detailed account of the philosophical debate on understanding, highlight common assumptions and intuitions as well as opposing positions and arguments, and I also consider philosophical work on related topics, in order to develop my arguments and position concerning the respective issue addressed in these chapters. Chapters five and six make up the second part of the book, as I answer the two main questions guiding my project, namely what scientific understanding is and how scientists achieve it. While my results from the first part of course contribute to the second part, my analysis and argumentation in chapters five and six are not as closely tied to the existing philosophical debate on understanding as the three preceding chapters.

As a general outcome, this book will amplify and further support recent developments within epistemology and philosophy of science as regards (scientific) understanding. My aim is to second the currently dominant view that understanding is an important intellectual achievement and goal of scientific research worthy of philosophical attention and analysis. Viewing understanding as something purely

subjective or psychological that has no legitimate place in the natural sciences, as argued by Droysen and Dilthey in the 19th century and by Hempel and other philosophers of science throughout the 20th century,is unjustifiedin light of theimportance attributed to understanding in scientific as well as everyday contexts. Valuing and researching understanding enables new perspectives and insights not only on scientific practice, but also the nature of knowledge and central epistemic goods more generally. But first things first, let us start by taking a look at some existing ideas and accounts of scientific understanding.

# **2. Different views on scientific understanding**

As already mentioned in the introduction, understanding has attracted the attention of epistemologists and philosophers of science only within the last 25 to 30 years. Since then, more and more philosophers have engaged with the investigation on understanding, be it scientific understanding in particular, or understandingin general. Asit can be expected, philosophers of science are primarily concerned with scientific understanding, whereas epistemologists turn to understanding as a general phenomenon or aim of human beings. However, these two philosophical disciplines talk to and with each other. Even epistemologists refer to scientific understanding quite often, as they take scientific understanding to be an especially valuable kind of understanding, maybe even the best kind of understanding one could achieve.The dialogue between philosophers of science and epistemologists is, hence, a very fruitful one. However, as this book focusses on scientific understanding, I will primarily rely on work done by philosophers of science, while I will also give epistemology its proper space in the course of my investigation.

In this chapter, I give an overview of three very important and influential accounts of scientific understanding. These are the accounts developed by Henk de Regt, Kareem Khalifa, and Finnur Dellsén. Based on this overview, I will highlight common assumptions shared by those three scholars, as well as disagreements among them concerning characteristics and the nature of understanding. The identification of commonalities of the three accounts will provide a basis for my own work on scientific understanding. And the detection of dissent and conflicting arguments will allow me to spotlight two questions that are of central importance for any analysis of scientific understanding.

Why do I only address these three accounts, although de Regt, Khalifa and Dellsén are by far not the only philosophers engaged in the discussions about understanding? While more and more epistemologists and philosophers of science join the debate about understanding, most of them focus on specific features of understanding,likeits relation to truth, toidealizations or to explanations, tomention just some examples. To my knowledge, de Regt and Khalifa are the only scholars so far who developed full-fledged and detailed philosophical accounts of scientific understanding that they presented, defended and publishedin form ofmonographs. Since their accounts are the most elaborated ones on the market, they certainly need to be considered in any philosophical investigation on scientific understanding. Additionally, I also include the account of scientific understanding developed by Dellsén. The reason to add this third account to the discussion in this section is that de Regt and Khalifa, despite all their differences, agree in one central aspect: they take explanation to be necessary for understanding.Their accounts only accommodate what is often called explanatory understanding. However, as I show in section 2.3 and especially in chapter three, there is no universal agreement that understanding requires explanation.On the contrary, accounts of understanding without explanation,most often called objectual understanding, are developed and defended in the literature. Therefore, I need to take an account of objectual understanding into consideration, and the one developed by Dellsén is a good representative for such accounts. Taken together, the accounts of scientific understanding from de Regt, Khalifa and Dellsén sufficiently represent the range of views concerning features that most scholars in the debate take to be crucial for understanding: abilities in general, grasping in particular, knowledge and explanation.

I do not address any account of understanding developed by epistemologists in this section, because epistemologists are usually interested in accounts of understanding in general, not with scientific understanding in particular. So, epistemologists aim at accounts that should accommodate understanding that any human agent could gain, not only scientists. While I do think that it might be possible to develop a unified or holistic account of understanding and that it is reasonable to expect some commonalities of scientific understanding and, let's say, laypeople's understanding,it is also plausible to expect some differences between scientific and other types of understanding. It is not the goal of this book to develop a general account of understanding that human beings can gain of anything. I happily leave this task to epistemologists. Instead, I want to develop an account of scientific understanding, the understanding that scientists achieve of the phenomena they are researching. Hence, I focus and only introduce three accounts of scientific understanding put forward by philosophers of science in this chapter. However, I will let epistemologists engaged in understanding have their say, especially in chapters three and four, where I discuss the relation of understanding and explanation as well as the nature of understanding.

But first, let us have a look what other philosophers of science think about scientific understanding. I start with Hend de Regt's account in section 2.1, followed by Kareem Khalifa's account in section 2.2, and by Finnur Dellséns's account in section 2.3. Finally, in section 2.4, I highlight in which aspects concerning understanding those three scholars agree, and on which they disagree and in what way. By doing so, I will point out that two crucial questions arise, and that I am going to answer these two questions in the course of this book. So, let's get started.

#### **2.1 Henk de Regt: Understanding phenomena through theories**

Henk de Regt was among the very first philosophers of science who were interested in understanding as a topic worthy of analysis for its own sake. Hence, he is something like a founding father of the philosophical engagement with understanding in contemporary philosophy. Any work on scientific understanding should consider de Regt's contribution. In his analysis, de Regt differentiates between two kinds of understanding crucial in science, which he characterizes as follows:

**UP:** understanding a phenomenon = having an adequate explanation of the phenomenon (relating the phenomenon to accepted items of knowledge)

**UT:** understanding a theory = being able to use the theory (pragmatic understanding)1

Additionally, he differentiates between three levels of science: the macro-level (that refers to science as a whole), the meso-level (that characterizes scientific communities) and the micro-level (corresponding to individual scientists). UT is intended to allow for micro-and meso-level variations, which means that different explanatory strategies are applied to achieve the macro-level aim UP.2

At the core of de Regt's account of understanding lies the thesis that scientists need intelligible theories if they want to gain scientific understanding of phenomena. If a theory is not intelligible for scientists, they will not be able to use the theory to construct an explanation of a phenomenon on the basis of the theory. Without understanding a theory, understanding a phenomenon is impossible.3 This leads de Regt to his criterion for understanding phenomena:

**CUP:** A phenomenon P is understood scientifically if and only if there is an explanation of P that is based on an intelligible theory T and conforms to the basic epistemic values of empirical adequacy and internal consistency.4

Whether a theory is intelligible or not depends on the epistemic framework that is accepted and provided by a scientific community. The available background knowledge and acquired skills determine whether a theory is intelligible. In different disciplinary, historical or social contexts, different theories are judged as being intelligible by scientists. To restrain the scientist's freedom to choose or construct any

1 De Regt, H. W. (2017), *Understanding Scientific Understanding.* New York, Oxford University Press, DOI: 10.1093/oso/9780190652913.001.0001, p. 91.

2 See ibid. pp. 90f.

3 See ibid. pp. 91f.

4 Ibid. p. 92.

kind of explanation based on any theory taken to be intelligible, de Regt adds the two epistemic values of empirical adequacy and internal consistency. Although it is not always obvious how these values should be applied, some degree of adequacy and consistency has to be reached by any explanation to secure a minimal scientific standard.5

De Regt anticipates possible critique to CUPin the form of putting too much emphasize on theories in the process of achieving understanding. Sometimes, scientists achieve understanding merely by experimentation that is independent of any theory. Additionally, there are scientific disciplines where explicit theories are absent. Finally, models constructed and used in science seem to provide understanding independently of any theory. De Regt's answer to these objections is that he does not require any theory to be full-fledged or explicitly articulated. Instead, he follows Giere6 and views a theory to be a collection of principles, which guide every form of observation, experiment, or model-construction. No scientific discipline works without some theoretical framework, no matter how explicit that might be.7

The account of scientific understanding developed by de Regt accommodates solely explanatory understanding, the understanding that is produced by a scientific explanation. Although he mentions that other forms of understanding exist, he does not cover or address them in his account. Rather, he simply presupposes their existence and characterizes them as types of knowledge. Since it is not possible in de Regt's framework to achieve explanatory understanding if there is no theory (no theoretical principles at all), theories are also viewed as a part of knowledge. De Regt employs a generic conception of explanation, which characterizes every explanation as an argument that presents a systematic line of reasoning that connects a phenomenon to accepted theoretical and empirical background knowledge. Hence, theories have to be part of the background knowledge.Otherwise, there will be nothing a phenomenon could be connected to, therefore there will be no explanation and, hence, also no explanatory understanding. An intelligible theoretical context is required for achieving explanatory understanding.8

Another argument that understanding and intelligibility are deeply intertwined is rooted in the fact that scientists understand the phenomena of their research by interacting and communicating with each other. If the theoretical principles, assumptions or models used by some scientists are not intelligible for others, science as a community will not make any progress. In most cases, scientists address and solve problems together in cooperation. Therefore, everything that contributes to the common activity of scientific research has to be intelligible for its members. De

5 See ibid. pp. 92f.

6 See Giere, R. N. (2006), *Scientific Perspectivism*. Chicago, University of Chicago Press, pp. 59–69.

7 See de Regt (2017), pp. 95ff.

8 See ibid. pp. 96–99.

Regt also describes the connection between his notion of intelligibility and the account of Humphreys9 , who introduces primary and secondary understanding. Primary understanding is achieved by an individual or group of scientists in isolation (would be identical to UT, having constructed an explanation), whereas secondary understanding requires communication and making the new constructed explanation intelligible to other individuals.10

Since achieving scientific understanding depends on intelligible theories, de Regt has to determine under which conditions a theory is intelligible. He wants to set some restrictions so that scientists do not decide on a purely subjective basis which theory is intelligible under which circumstances. If a theory is intelligible, i.e. if scientists understand the theory, they will have to have some idea of how the theory functions or how it produces certain outputs. Since de Regt allows for a wide variety of theories (for various degrees of exactness), he allows for a variety of criteria to assess the intelligibility of a theory.11 He offers one possible criterion:

**CIT1:** A scientific theory *T* (in one or more of its representations) is intelligible for scientists (in context *C*) if they can recognize qualitatively characteristic consequences of *T* without performing exact calculations.12

By including the individual scientists and the specific context, CIT1 accommodates the pragmatic and context-dependent nature of the intelligibility of theories, and, hence, also of UT and UP, since both notions depend on the intelligibility of theories. Besides the particular qualities of the theory in question, the combination of established scientific practices in a certain field, the developed abilities or skills of the individual scientists, and the established and available background knowledge determine whether a theory is intelligible for an individual scientist or group of scientists, or not. Certain qualities of a theory provide tools only if the skills of a scientist are attuned to these qualities.13

The two criteria proposed by de Regt, CUP and CIT1, constitute the basis of his philosophical theory of understanding.Understanding, explanation,and prediction are viewed to be interrelated goals of science. He claims that prediction is not possible without understanding. If a scientist does not understand the important features and structure of a theory, if the theory is not intelligible to her, she will not be able to produce successful predictions. Instead, she will merely be guessing. A successful prediction that can be explained by a scientist shows that she understood a

9 See Humphreys (2000), p. 269.

10 See de Regt (2017), pp. 99f.

11 See ibid. pp. 101f.

12 Ibid. p. 102.

13 See ibid. p. 103.

theory. Hence, predictions enter de Regt's account of understanding through CIT1, according to which scientists must be able to recognize qualitative characteristic consequences of a theory. And crucially, both kinds of understanding, UT as well UP, cannot be achieved by performing a rule-following procedure. Instead, tacit skills, the know-how to make use of a theory or an explanation, are required. Which skills a scientist needs to make a theory intelligible to her depends on the qualities of the theory. By applying CIT1, it is possible to check whether the appropriate skills for a specific theory are present.14

In making decisions or performing reasoning, humans often refer to intuitions. Intuitions, in de Regt's view, can be defined as judgements whose underlying reasons are not fully accessible for a subject and which are results of heuristics that have been developed in an evolutionary process. The human cognitive system has produced these heuristics in response to environmental influences. It is possible to develop reliable intuitive skills in an environment that is sufficiently stable to make successful predictions if a subject has the opportunity to learn these regularities through practice. These conditions are usually fulfilled in science. Therefore, the skills acquired by scientists allow them to intuitively recognize theoretical consequences of a theory. For achieving scientific understanding, skills and intuitive judgements are crucial.15

If a theory is intelligible to scientists because its theoretical qualities match their skills, they can reason "intuitively" with it. Like our everyday intuitive skills, scientists' skills are the outcome of a complex learning process in which they find themselves (that is, the historical and disciplinary context of their science).16

As de Regt has already mentioned, the construction of models or of explanations more generally is a matter of skill, of pragmatic decisions which lead to the desired result. Scientists have to have the know-how, the ability, to address and solve a new problem.17 There are no fixed general rules that guide every possible construction process, or so many different rules that it is impossible to pick the right ones out of a big catalogue. Various theories as well as models of scientific explanation provide different tools for understanding, and all of them might be legitimately used in certain circumstances or contexts.18 Hence, de Regt is an explanatory pluralist.

De Regt wants to clarify in the framework of his theory how precisely understanding and intelligibility are related to certain contexts. In short, the context determines which tools are available or deemed suitable. Which contextual factors are

14 See ibid. p. 107f.

15 See ibid. pp. 109ff.

16 Ibid. p 110.

17 See ibid. p. 112.

18 See ibid. p. 115.

important? According to de Regt's theory, certain qualities of a theory are conducive to its empirical success because they enhance the intelligibility of a theory for those scientists who possess the skills to use the conceptual tools that are associated with these qualities. Since science is a community activity and scientific understanding is a community achievement, the conceptual tools are mostly established at the level of scientific communities (meso-level). In a sense, understanding a theory means to become familiar with it. As soon as a scientist has developed the relevant skills to use the theory in an intuitive way (CIT), the theory is familiar to her. More specifically, the tools have to be familiar to the users. If scientists have developed the relevant intuitive skills to use these tools, the tools are familiar to the scientists and they are able to make successful predictions, which improves the intelligibility of the theory.19

Within the literature on scientific explanation, one finds pragmatic theories of explanation, which also allow for a plurality of explanatory strategies in scientific practice.20 Such theories are based on the idea "that explanations are given and received by particular people in particular contexts for particular purposes. Different contexts, people, and purposes may require different types of explanation."21 De Regt focuses on the pragmatic theory of Bas van Fraassen22, who considers explanations to be answers to why-questions. But a why-question alone cannot determine what kind of answer is asked for. Additionally, the context has to be taken into consideration to make sense of the question and to know what kind of answer is adequate. Philip Kitcher and Wesley Salmon23 have criticized van Fraassen's theory because he does not give criteria on when a factor is explanatorily relevant. Although van Fraassen states that explanatory relevance requires scientific relevance and explicates under which conditions an answer is scientifically relevant, he also states that not all scientifically relevant factors are explanatorily relevant, which leaves the problem unsolved. The context determines which scientifically relevant factors are also explanatorily relevant. By adding the two basic epistemic values, de Regt wants to solve van Fraassen's problem. Only if an explanation conforms to internal consistency and empirical adequacy, will it be explanatorily relevant.24

Summing up, de Regt covers two different kinds of scientific understanding with his theory, which are UT and UP. Scientists need to have intelligible theories, need to understand theories, if they want to understand phenomena. On the basis of an intelligible theory, scientists can construct explanations of phenomena, and

19 See ibid. pp. 116–119.

20 See ibid. p. 123.

21 Ibid. p. 124.

22 See van Fraassen, B. C. (1980), *The Scientific Image*. Oxford, Clarendon Press, DOI: 10.1093/0198244274.001.0001, especially chapter 5.

23 See Kitcher, P. & Salmon, W. C. (1987), "Van Fraassen on explanation." *Journal of Philosophy*, 84 (6), pp. 315–330, DOI: 10.2307/2026782.

24 See de Regt (2017), pp. 125–128.

hence understand them. Whether any theory is intelligible for some scientist and which type of explanation is constructed depends on the context, the skills of the individual researcher as well as the practices accepted by the respective community. De Regt presents three extensive case studies from the history of physics to substantiate and illustrate his theory of understanding.

The analysis of scientific understanding provided by Henk de Regt focusses on explanatory understanding, which is legitimate, but he does not give explicit arguments on whether, and if so why, explanatory understanding is the most important or general kind of understanding or how explanatory understanding is related or incorporated into other forms of understanding. In contrast to de Regt, Kareem Khalifa explicitly addresses the relation between explanatory and objectual understanding. So, let us have a look at Khalifa's account of scientific understanding, which varies significantly from de Regt's theory in several ways.

## **2.2 Kareem Khalifa: Scientific understanding is scientific knowledge of an explanation**

Khalifa develops a model of understanding that he labels EKS model of understanding (explanation, knowledge, science model), since these three concepts are crucial for his account. Before talking about the details of this model of understanding, it is important to recognize two crucial features of it: First, Khalifa explicitly includes the fact that understanding is gradual in his account. That is, he provides a framework that incorporates the fact that understanding comes in degrees. De Regt's theory does not accommodate this. Khalifa's theory of understanding shall allow for the possibility to compare the understanding of different individuals, he develops a comparative account of understanding, while he does not provide a quantitative analysis of degrees of understanding. This is probably impossible. Rather, he takes it to be sufficient that in certain situations it is possible to decide which subject has a better understanding.25 Second, Khalifa is only concerned with explanatory understanding, or understanding-why.26 This is a common aspect of the theories of de Regt and Khalifa.

His principle of better understanding, how Khalifa calls it, takes the following form:

25 See Khalifa (2017b), chapter 1.

26 See ibid. pp.2f.

*EKS1*: *S1* understands *why p* better than *S2* if and only if:

Let's consider the EKS-model in more detail. The first principle (A) is called *Nexus Principle*. Khalifa starts with the idea that the subject's understanding of a phenomenon increases if she knows more correct explanatory factors that contribute to the phenomenon, and if she knows more of the relations that exist between these factors. On this basis, Khalifa defines the explanatory nexus of a phenomenon *p* as "the set of correct explanations of *p* as well as the relations between those explanations."28

If the explanatory nexus of *p* only includes correct explanations, how can it be determined whether an explanation is correct? Khalifa presents these four conditions:

*q* (correctly) explains *p* if and only if:

Notice that *q* denotes the explanans, the statement that does the explaining of *p*.The fourth condition is crucial: like de Regt, Khalifa explicitly allows for an explanatory pluralism. He does not give a strict definition of explanation. In fact, he even allows to identify 'explanation' with 'explanatory information'. With local constraints he refers to the specific interest of the researcher, the established standards of the discipline, and so on. Local constraints are context-dependent. Like de Regt, Khalifa wants to formulate an account of understanding that is universally valid, but allows for contextual variation. Khalifa reaches this goal by formulating three global conditions and one local condition for understanding.30

The explanations belonging to one explanatory nexus can stand in in many varying relations to each other, and the grasp of an explanatory nexus is more complete if more explanations and inter-explanatory relations are grasped, if the quality or importance of the explanations and inter-explanatory relations are grasped, or if more details of the explanations and inter-explanatory relations are grasped. Again,

27 Ibid. p. 14.

28 Ibid. p. 6.

29 Ibid. p. 7.

30 See ibid. pp. 6ff.

this model of understanding is not supposed to offer a quantitative analysis of understanding. All the dimensions just mentioned, quantity, quality and the level of detail of explanations and inter-explanatory relations, figure into understanding, and it depends on the specific context or situation which dimension of one's grasp is more important.31

The second principle (B) is the *scientific knowledge principle*.This principle captures everything Khalifa takes to be necessary for a characterization of grasping. He defines grasping as "a cognitive state bearing some resemblance to scientific knowledge of some part of the explanatory nexus."32 This implies the question: what is scientific knowledge? Khalifa offers this definition: "*S* has scientific knowledge that *q* explains *why p* if and only if the safety of *S*'s belief that *q* explains *why p* is because of her scientific explanatory evaluation."33 In short, knowledge counts as scientific knowledge if it has been gained by a scientific explanatory evaluation, SEEing. According to Khalifa, SEEing consists of three components: the consideration of plausible potential explanations of the phenomenon of interest, the comparison of the potential explanations, and finally of the formation of (doxastic) attitudes based on the comparisons. SEEing ensures the safety of one's explanatory commitments and therefore the status of this kind of knowledge as scientific. The grasp of a subject bears greater resemblance to scientific knowledge along the following dimensions: the number of plausible potential explanations the agent has considered, the number of considered explanations that have been compared using scientifically acceptable methods and evidence, the scientific status of these methods and evidence that has been used, the safety of the agent's beliefs about explanations, the accuracy of the agents beliefs about explanations, and finally the variety of ways that the agent can use explanatory information so as to achieve different scientific goals.34

To avoid that principles (A) and (B) of the EKS-model could come into conflict with one another, the *ceterisparibus* clauseis used.35 Either S1 graspsmoreitems of *p*'s explanatory nexus(i.e. she knowsmoreitems that belong to the nexus) than S2,while both are equally competent in a specific scientific field, or the grasp (i.e. knowledge) of S1 ismore scientific than the grasp of S2, e.g.if S1 is a professorin a certain domain and S2 a very interested lay person.

In sum, Khalifa's account of scientific understanding stands in the tradition of the "received view" of understanding, as Khalifa calls it,36 and he provides this definition of the received view:

31 See ibid. pp. 9f.

32 Ibid. p. 11.

33 Ibid. p. 12.

34 See ibid. p. 11ff.

35 See ibid. p. 15.

36 See ibid. p. 16.

*S* understands *why p* if and only if there exists some *q* such that *S* knows that *q* explains *why p*. 37

That is Khalifa's view on scientific understanding. Let us now look at a third alternative.

#### **2.3 Finnur Dellsén: Understanding as dependency modelling**

The third account I want to introduce is the one offered by Finnur Dellsén. His account differs significantly from the other two accounts just presented, since Dellsén argues for understanding without explanation, namely an account of objectual understanding. To begin with, Dellsén points to some features of objectual understanding. First, he specifies objectual understanding as understanding of phenomena. Dellsén is not interested in understanding topics, subject matters or theories, as some other advocates of objectual understanding do38, because he wants to avoid the slip form understanding something to understanding a discipline that studies or an account that refers to the thing or phenomenon that is to be understood. Second, understanding is gradual in a way that propositional knowledge is not. Subjects can understand a phenomenon to different degrees and the degree of understanding of a phenomenon of one subject can change over time. This is a widely, I would even say universally, accepted feature of understanding. And third, Dellsén assumes that paradigmatic cases of objectual understanding can be found in the empirical sciences. Therefore, he takes his account to be an account of scientific understanding.39 Given these characterizations of the kind of understanding that Dellsén is concerned with, it is justified to assume that Dellsén is dealing with the same kind of understanding as de Regt and Khalifa: the understanding of phenomena achieved by scientists.

Dellsén's "account of understanding […] holds that to understand a phenomenon is to grasp a specific kind of model of that phenomenon's dependence relations."40 He calls his account 'dependence modelling account', DMA for short. Models, in

37 Ibid. p. 18.

38 Like Christoph Baumberger for instance, see Baumberger, C. (2011), "Types of Understanding: Their Nature and Their Relation to Knowledge." *Conceptus*, 40, pp. 67–88, DOI: 10.1515/cpt-2 014-0002; and Baumberger, C. & Brun, G. (2017), "Dimensions of Objectual Understanding." In Grimm S. R., Baumberger, C. & Ammon, S. (eds*.), Explaining Understanding. New Perspectives from Epistemology and Philosophy of Science*, pp. 165–189, New York and London, Routledge.

39 See Dellsén, F. (2020), "Beyond Explanation: Understanding as Dependency Modelling." *Brit. J. Phil. Sci.*, 71, pp. 1261–1286, DOI: 10.1093/bjps/axy058, pp. 1263f.

40 Ibid. pp. 1264f.

Dellsén's view, are information structures of some kind that are interpreted so as to represent the target.

These information structures can be concrete, as in Watson and Crick's original model of DNA, or abstract, as in mathematical or computational models like the Lotka-Volterra model of predation in ecological systems. In both cases, the structures are associated with an intended interpretation that specifies how the different parts of the structure correspond to different elements and relations in the phenomenon – a 'key'.41

Importantly, no information structure, may it be a material object or a system of equations, is a model in itself. Only through the interpretation of (parts of) these concrete or abstract information structures do they become part of a model.42 Parts of the information structure must be associated with specific parts of the phenomenon in order to be a model of that phenomenon. Additionally, as understanding takes place in the mind of individuals, the models that are used for understanding a phenomenon must somehow be related to (human) thought. Dellsén does not analyze in detail what the relation between models and mind might be, but rather uses the term 'grasp' for referring to this relation.43 That is, in the opinion of Dellsén, "understanding consists of grasping a certain kind of model of the understood phenomenon."44

"What kind of model must an understanding agent grasp?"45 Since models are always incomplete or inaccurate representations, which aspects of a phenomenon must be represented in a model that enable understanding? Based on former work that relates understanding-why with dependence relations, Dellsén states "that the aspects of a phenomenon that matter for understanding are the dependence relations that the phenomenon, or its features, stands in towards other things."46 He

43 See ibid. p. 1265.

45 Ibid. p. 1266.

41 Ibid. p. 1265. Dellsén uses the notion of a 'key' from Frigg and Nguyen, see Frigg, R. & Nguyen, J. (2016), "The Fiction View of Models Reloaded." *The Monist*, 99, pp. 225–242, DOI: 10.1093/m onist/onw002.

42 Dellsén is following Weisberg in viewing models as interpreted structures. The kind of modelling that Dellsén is thinking of resembles Weisberg's 'target-directed modelling'. For more information, see Weisberg, M. (2013), *Simulation and Similarity. Using models to understand the world*, Oxford, Oxford University Press DOI: 10.1093/acprof:oso/9780199933662.001.0001, especially chapter 5.

44 Ibid. p. 1265.

46 Ibid. p. 1266. Dellsén is referring here to Kim, J. (1974), "Noncausal Connections." *Noûs*, 8, pp. 41–52, DOI: 10.2307/2214644; and Greco, J. (2014), "Episteme: Knowledge and Understanding." In Timpe, K. & Boyd, C. A. (eds.), *Virtues and Their Vices*, pp. 285–302, Oxford, Oxford University Press, DOI: 10.1093/acprof:oso/9780199645541.003.0014; and Grimm, S. (2014), "Un-

does not limit the notion of dependence relations to causality, but allows for various kinds of dependence relations to hold between (parts of) phenomena, for example grounding relations or mathematical relations.47 "The kind of model that [he] think[s] is involved in understanding is one that aims to capture the network of dependence relations that a phenomenon stands in, whatever these relations turn out to be. [He] will refer to this as a 'dependency model'."48

However, Dellsén does not take grasping any dependency model of a phenomenon as being enough for understanding that phenomenon. "Rather, the model must in some sense be a 'good' representation of the relevant dependence relations."49 The straightforward suggestion is that the quality of a model depends on the extent to which the model correctly depicts the network of dependence relations of a phenomenon. Yet, a dependency model can fail in two respects in depicting the network of dependence relations, either by incorrectly representing (misrepresenting) some aspects of the network (idealization) or by not representing certain aspects at all (abstraction). Hence, Dellsén recognizes two distinct criteria: accuracy and comprehensiveness. These criteria might come into conflict, the increase of the one might require the sacrifice of the other. As understanding depends on both criteria, it is possible to increase one's understanding by sacrificing one of the two criteria sometimes, given that this brings sufficient benefit in terms of the other criterion, according to Dellsén. Thus, his model-based account can explain the gradual nature of understanding in terms of two other gradable notions, namely accuracy and comprehensiveness.50

A final important concept in Dellsén's account of understanding is context, which has several functions. First, any context determines a threshold for the degree of understanding. Attributing understanding of a phenomenon to a subject requires that the subject grasps a sufficiently accurate and comprehensive model of the phenomenon, so that the understanding exceeds the contextually determined threshold. Second, any context specifies which parts of a complex phenomenon have to be sufficiently understood in order to understand the phenomenon itself. Ecologists, physicians and psychologists will all understand human mating, but in different ways. And third, the context also designates which (parts of) other phenomena are striking enough so that their dependence relations to the target

derstanding as Knowledge of Causes." In Fairweather, A. (ed.), *Virtue Epistemology Naturalized: Bridges between Virtue Epistemology and Philosophy of Science*, pp. 347–360, Dordrecht, Springer, DOI: 10.1007/978-3-319-04672-3\_19. Dellsén argues that objectual understanding can come apart from explanation, which is not possible in the view of Greco and Grimm, at least not according to Dellsén's reading of their work.

47 See ibid. p. 1266.

48 Ibid. p. 1266.

49 Ibid. p. 1267.

50 See ibid. p. 1267.

phenomenon, or lack thereof, become relevant for the understanding of the target phenomenon. For example, one does not need to consider the whole history of western societies to understand the length of the shadow of a flagpole at a certain time, but one should have some basic knowledge from physics and geometry.51

In short, Dellsén proposes the following dependency modelling account (DMA) of understanding:

DMA: *S* understands a phenomenon, *P*, if and only if *S* grasps a sufficiently accurate and comprehensive dependency model of *P* (or its contextually relevant parts); *S*'s degree of understanding of *P* is proportional to the accuracy and comprehensiveness of that dependency model of *P* (or its contextually relevant parts).52

DMA does not require explanation, although Dellsén takes dependence relations to usually undergird explanations. He contrasts his DMA with explanatory accounts of understanding, which he summarizes in the following way:

*U*→*E*: *S* understands *P* only if *S* grasps enough of an adequate explanation of *P* (or its relevant features); other things being equal, *S* has more understanding of *P* to the extent that *S* grasps more of an adequate explanation of *P* (or its relevant features).53

*U*→*E* is intended to capture any account of explanatory understanding that takes explanation as a necessary requirement for understanding. Dellsén then discusses three cases in which, according to him, *U*→*E* fails to accommodate the understanding that scientists achieve, whereas DMA can cope with such types of cases. I will engage with these three cases in detail in section 6.2.3, but now, let's recap the three different accounts of scientific understanding.

## **2.4 Two questions concerning scientific understanding**

So, what shall we make of these three different accounts of scientific understanding? All of them share some common ground. First, they are all intended to conceptualize scientific understanding as an understanding that is gained in *sciencein general*, or in science as a whole, and do not distinguish between different scientific disciplines. Some fundamental unity of science seems to be assumed by de Regt, Khalifa, and Dellsén. In this book, I take up this assumption and will be concerned with a general

51 See ibid. pp. 1267f.

52 Ibid. p. 1268.

53 Ibid. p. 1269.

account of scientific understanding that will be able to accommodate all scientific disciplines,or as many as possible, by pointing out commonalities, while still leaving room for differences between disciplines. Second, however, the criteria, principles, or definitions of understanding presented by the three scholars refer to understanding that*individual* scientists achieve.The only exception is de Regt's CUP, which does not refer to individuals specifically. However, if one takes a look at the case studies that de Regt provides, one will see that he is investigating whether certain individual scientists understood some phenomenon, not only some theory.While de Regt does mention that science can be divided into a macro-, meso-, and micro-level, he does not analyze in which regards understanding of phenomena differs with respects to these three levels. So, all three scholars introduced in this chapter take understanding to be some achievement that can be gained or realized (primarily) by individuals. Third, all accounts address understanding of phenomena achieved in science or take understanding of phenomena as an ultimate aim of science. While other types of understanding might be necessary for understanding phenomena, like the understanding of theories or models used in research, the most important and interesting type of understanding in science is the understanding of the phenomena that are investigated. Hence, I will focus on the understanding of phenomena, too. And fourth, all three scholars agree that understanding is context-dependent, that the historical and disciplinary circumstances or local constraints have an impact on the achievement of understanding and the assessment of its quality. I will take this insight into account as well.

So much for the agreement and commonalities of the three accounts. Yet, they also differ in crucial respects. For instance, de Regt takes scientific understanding to be some kind of ability or know-how, since he argues that scientists need to *be able* to use a theory to construct an explanation of a phenomenon. If scientists are unable to construct an explanation, they will not have understood the phenomenon. Khalifa, in contrast, claims that scientific understanding is scientific knowledge of an explanation, and not an ability. And in Dellsén's view, scientific understanding is the ability to grasp a 'good' dependency model of some phenomenon, an ability that does not require explanation. So, de Regt and Khalifa agree that understanding requires explanation, a feature that is denied by Dellsén. However, de Regt and Dellsén both take understanding to be an ability and not a kind of knowledge, as Khalifa explicitly claims. The comparison of these accounts highlights that at least two questions about scientific understanding are of central interest, but not ultimately resolved within the debate. These two questions are:

In order to answer the main research questions of this book, what scientific understanding is and how scientists achieve it, I have to address the two questions identified through the comparison of the three accounts of understanding. That is because answers to my main research questions will depend on the answers one gives to the other two questions just mentioned. If understanding requires explanation, some explanation must somehow beinvolved or related to the understanding,mayit be as a starting point or a product. If understanding does not require explanation, scientists will not have to draw on or produce any explanation for understanding, and hence might acquire the latter in quite a different way than if some explanation would be involved. Furthermore, if understanding is some ability, a type of knowing-how, it might have quite different characteristics than if it would be some form of propositional knowledge or knowledge-that. Moreover, the acquisition processes of knowing-how and knowing-that are very different from one another, as various scholars have already pointed out. This issue will be the topic of section 4.1.

So, in sum, depending on whether scientific understanding requires explanation in some way or not and whether understanding is an ability or a form of propositional knowledge, the way how scientists actually acquire understanding of phenomena will turn out to be fairly different. Hence, it is necessary to first provide answers to the questions concerning the relation of understanding and explanation and the nature of understanding, that is, whether understanding is an ability or a type of knowledge. Only then can the third question, how scientists actually achieve scientific understanding, be answered.Thus, these three questions are the ones I am going to answer in this dissertation. I will start with the question concerning the necessity of explanation for understanding, which will be answered in chapter three. I then turn to the nature of understanding in chapter four. The third question, which I take to be the most interesting one, will be answered in the course of chapters five and six. But first things first, let us start with looking at explanation and its potential role in understanding.

# **3. Scientific understanding, scientific explanation, and why they cannot be torn apart**

The connection between understanding and explanation is a core topic in the debate about understanding, especially for philosophers of science.The presentation of the accounts of scientific understanding developed by Henk de Regt, Kareem Khalifa and Finnur Dellsén in the previous chapter exemplify this claim. On the one hand, the accounts of understanding from de Regt as well as Khalifa are only concerned with explanatory understanding, a type of understanding that is tied to explanation. De Regt admits that kinds of understanding without explanation exist, but his account of understanding is not intended to cover these kinds. In contrast to de Regt, Khalifa explicitly argues that at least one other kind of understanding, namely objectual understanding, can be reduced to explanatory understanding. On the other hand, Dellsén presents an account of scientific understanding in terms of objectual understanding, according to which explanation is not necessary for understanding. What should we make of these different positions? Does scientific understanding require explanation or not?

In this chapter, I argue that scientific understanding does require explanation. To do so, I first address the concept of explanation. Explanation is one of the core concepts in philosophy of science and various accounts and definitions of explanation have been providedin the last decades. To avoid confusion, I need to clarify what I mean by the concept and the term 'explanation'. Hence, I start with a very brief discussion of explanation in section 3.1, in which I introduce the generic conception of explanation that I adopt throughout this book. I then turn to the main topic of this chapter, the relation of scientific understanding and explanation. I do so by discussing arguments that are proposed to support a view of understanding that is independent of explanation. In section 3.2, I present and critically discuss Peter Lipton's view on understanding without explanation. I analyze the four examples that Lipton provides as instances of understanding without explanation and argue that none of the examples succeeds in being an instance of understanding without explanation. Subsequently, I delve into the discussion about two forms of understanding that some authors strictly distinguish, namely, objectual and explanatory understanding. In section 3.3, I present the view of Jonathan Kvanvig, who argues that

explanatory and objectual understanding are intrinsically different and the counterarguments from Khalifa against Kvanvig. I argue that Khalifa's critique of Kvanvig's conception of objectual understanding is in line with my criticism on Lipton's view. As the accounts from Lipton and Kvanvig are unrelated while facing the same problems, a conception of scientific understanding without explanation becomes more and more implausible. Finally, in section 3.4, I engage with further arguments in favor of and against a separation of objectual and explanatory understanding. Christoph Baumberger wants to distinguish objectual and explanatory understanding in terms of their targets and vehicles. Following Stephen Grimm's argument why a distinctionin terms of the targets of understandingis not possible, I will argue that the distinction in terms of the vehicle is not possible either. I conclude that, at least for scientific understanding of phenomena, a differentiation between objectual and explanatory understanding is not reasonable, as both terms, in their prevalent use, cannot accommodate scientific practice and the function of explanation within it. Hence, scientific understanding is not possible without explanation.

One important remark is necessary before the analysis of the relation of understanding and explanation. Although I am exclusively dealing with scientific understanding of phenomena, understanding that is gained in the scientific domain, many authors in the debate are concerned with understanding in general and do not reduce their analysis to scientific understanding. The controversies about understanding and explanation, about objectual and explanatory understanding, which I examine in this chapter, are also not restricted to scientific understanding. However, this is not a problem for my project. I analyze the plausibility of arguments in favor of an independence of understanding from explanation for the scientific domain, whether it makes sense for science to conceptualize scientific understanding as being independent from explanation. I am not claiming that any type or kind of understanding requires explanation. In fact, I do think that there are types of understanding that are independent of explanation. But these types will not be typical or distinctive as an aim of science, so I shall argue. Therefore, any argument concerning the relation of understanding and explanation needs to be interpreted in light of scientific practice if scientific understanding as an aim of science is the target of investigation. Having this clarification in mind, I do not take it to be problematic that scientific understanding is not always clearly distinguished from other types of understanding by all authors.

#### **3.1 A few words on explanation**

Prior to delving into the discussion of whether understanding requires explanation, some considerations concerning the concept 'explanation' are necessary. Explanation has been and still is one of the most central concepts in philosophy of science. As Henk de Regt nicely puts it, even "after sixty years of debate about scientific explanation, there is currently no consensus favoring one model but rather a plethora of different models of scientific explanation."1 Among the types of explanation that are proposed and discussed are deductive-nomological, unificationist, model-based, causal, counterfactual, mechanistic, functional, probabilistic, or mathematical explanations, and this list is not exhaustive. Some of these types overlap, some can or might be reduced to another type.2 Since I am concerned with scientific understanding, and not with scientific explanation, I do not attempt to develop and provide a specific conception of scientific explanation. This issue would be more than enough for another research project. However, I do adopt a generic conception of explanation. In this section, I delineate the basic features of this generic conception of explanation.

What is an explanation? Attempts to answer this question led to the emergence of two main opposing camps: adherents of an ontic conception of explanation versus proponents of an epistemic conception.While according to the ontic conception explanations are things or facts that exist or take place in the world, the epistemic conception suggests that explanations are (complexes of) representations of things or facts in the world. Consequently, for the ontic conception explanations exist independently of any cognitive subjects, whereas the epistemic conception requires subjects to construct explanations, representations, of things in the world. As no decisive argument in favor of or against one of the two conceptions could be provided so far, I follow my intuition and adopt an epistemic conception of explanation. In my view, it is more plausible to speak of things like entities, phenomena, events, or structures to be in the world, while explanations are constructed to represent these things. Explanations are created by subjects and if there were no subjects trying to explain things in the world, these things would still exist, but there would be no explanations.3

So, for the purpose of this book, explanations are representations.The next question is what makes a representation an explanation and not merely a description. In this regard, I follow Hayne Reese and, very roughly, view explanations to pro-

1 De Regt (2017), p. 49.

2 For an overview on the different types of scientific explanation, see for example Woodward, J. & Ross, L., "Scientific Explanation", *The Stanford Encyclopedia of Philosophy* (Summer 2021 Edition), Edward N. Zalta (ed.), URL = https://plato.stanford.edu/archives/sum2021/entries/scie ntific-explanation/ (last accessed April 12th, 2022).

3 For one line of argumentation against the ontic and in favor of the epistemic conception of explanation, see Wright, C. & van Eck, D. (2018), "Ontic Explanation Is either Ontic or Explanatory, but Not Both.*" Ergo: An Open Access Journal of Philosophy*, 5, pp. 997–1029, DOI: 10.3998/e rgo.12405314.0005.038.

vide reasons for *why* something is the case or could be the case,4 while descriptions merely state what *is* the case. Descriptions provide us with facts (e.g. the sky is blue and blue light is scattered more than other colors by the atmosphere), while explanations give reasons for these facts (the sky is blue, *because* blue light is scattered more than other colors by the atmosphere). An explanation transcends a description, as a representation "becomes explanatory because it goes beyond the question answered by description – "What happens?" – to the question answered by explanation – "Why does it happen?"".5 The notion of reasons is deliberately kept vague, in order to capture all kinds of reasons that are deemed crucial or adequate in different contexts. Reasons include causes, but they are not limited to causes, as not all types of explanation refer to an actual cause of a phenomenon. Famously, unificationist explanations provide unified accounts of various different phenomena by deriving descriptions of as many different phenomena as possible from as few argument patterns as possible, to use Philip Kitcher's technical vocabulary, but without referring to any actual causes of some phenomenon.6

De Regt and Khalifa, despite their differences with respect to understanding, agree on one crucial aspect: they allow for an explanatory pluralism to achieve understanding. Both authors argue that, depending on the historical or disciplinary context, various explanatory strategies lead to understanding. Following a review of various types of explanation, de Regt "conclude[s] that understanding is a universal aim of science that can be achieved by contextually varying modes of explanation."7 And Khalifa claims that an explanation must "satisfy "local constraints" […] [as] the relevance of many explanatory features depends on the specific explanandum, the standards of the discipline, and the interest of the inquirer."8 Hence, there is not one kind of explanation that provides the best or most accurate understanding in

4 I am referring here to the concept of how-possibly explanations, explanations that do not explain why something actually happened, but rather explain how something is or was possible. Yet, whether how-possibly explanations should be seen or treated as genuine explanations is a contested question, which I will not address here. For more information, see for example Brainard, L. (2020), "How to Explain How-Possibly." *Philosophers Imprint*, 20 (13), pp. 1–23; or Reydon, T. (2012), "How-possibly explanations as genuine explanations and helpful heuristics: A comment on Forber." *Studies in History and Philosophy of Biological and Biomedical Sciences*, 43 (1), pp. 302–310, DOI: 10.1016/j.shpsc.2011.10.015.

5 Reese, H. W. (1999), "Explanation Is Not Description." *Behavioral Development Bulletin*, 8 (1), pp. 3–7, DOI: 10.1037/h0100524, p. 4.

6 For Kitcher's account of unificationist explanation, see e.g. Kitcher, P.(1989),"Explanatory Unification and the Causal Structure of the World." In Kitcher, P. & Salmon, W. (eds.), *Scientific Explanation*, Minnesota Studies in the Philosophy of Science, Vol. 13, pp. 410–505, Minneapolis (MN), University of Minnesota Press.

7 De Regt (2017), p. 86. His full review of different models of explanation can be found ibid. chapter 3.

8 Khalifa, (2017b), p. 8.

all cases. Instead, the subjects involved in a process of gaining understanding must assess, according to the relevant standards that they follow, which explanation is the 'best'or appropriate one to lead to understanding in the respective context. Since the pluralist positions concerning explanation of de Regt and Khalifa are supported by a growing attention and literature on explanatory pluralism and diversity in science,9 I adopt a pluralist position of scientific explanation as well.While being an explanatory pluralist, I do think that a generic conception of explanation, which leaves room for the various types of scientific explanation that can be found in scientific practice, can be articulated.10 Hence, I provide the following conception of explanation:

An explanation is a representation of relations of (parts of) the phenomenon under investigation, which provides reasons (an explanans) for features of (parts of) the phenomenon (the explanandum).11

This is the generic conception of explanation that I use and refer to when I speak about explanation in the remainder of this book. Again, I use the notion 'reasons' in this conception in order to include non-causal explanations, like unificationist, lawbased, probabilistic, logical and further types of explanations. Having clarified what I mean by explanation, we can now turn to the actual topic of this chapter. Namely, the relation of understanding and explanation.

## **3.2 Cases of understanding without explanation?**

Some philosophers in the debate on understanding maintain that in some cases, understanding can be gained without explanation. Peter Lipton is one of them. I

9 See for example Mantzavinos, C. (2016), *Explanatory Pluralism*. Cambridge, Cambridge University Press, DOI: 10.1017/CBO9781316440599; or Braillard, P.-A. & Malaterre, C. (2015), *Explanation in Biology. An Enquiry into the Diversity of Explanatory Patterns in the Life Sciences.* In History, Philosophy and Theory of the Life Sciences, Dordrecht, Springer, DOI: 10.1007/978-94 -017-9822-8; or Weber, E., de Regt, H. W. & van Eck, D. (2021), "Investigating the Unity and Disunity of Scientific Explanation." *Found Sci*, 26, pp. 1021–2024, DOI: 10.1007/s10699-020-09704 x; or Rice, C. & Rohwer, Y. (2021), "How to Reconcile a Unified Account of Explanation with Explanatory Diversity." *Found Sci*, 26, pp. 1025–1047, DOI: 10.1007/s10699-019-09647-y.

10 I got the idea of formulating and using a generic conception of explanation from de Regt, who also provides a generic conception of explanation, though a different one. Cf. de Regt (2017), pp. 24f.

11 Note that I am concerned with scientific understanding of phenomena that are the targets of scientific investigations in this book and that I will not analyze what it means to understand a theory scientifically. Hence, I stay agnostic as to whether this generic conception of explanation is applicable to understanding other objects than phenomena, like for example theories.

present Lipton's examples, which he simply calls causation, necessity, possibility, and unification, and argue that he fails to show that scientific understanding is possible without explanation. Either he is wrong in claiming that no explanation is involved in the discussed cases, or he does not make a convincing point that his arguments are applicable to or can accommodate scientific understanding.

Before I address Lipton's arguments that there are cases of understanding without explanation, I want to mention some general aspects concerning Lipton's view of understanding. First, he is not exclusively concerned with scientific understanding, or at least he does not say so explicitly. Hence, I take it that Lipton is engaged in the analysis of understanding more generally and I have to analyze whether his view is plausible for science. Second, Lipton identifies understanding with the cognitive benefits that an explanation provides. These cognitive benefits are, in turn, identified as kinds of knowledge, including knowledge of causes, of necessity, of possibility, and of unification. In short, Lipton takes understanding to be certain kinds of knowledge that are provided by explanations. Importantly, understanding is not identified with the explanation itself, but rather with its benefits. This point is crucial, as it enables a separation of understanding and explanation.12 As I have not addressed the question of whether understanding should be conceptualized as a kind of knowledge (-that) or rather as an ability (knowledge-how), which I do in chapter four, I adopt Lipton's conception of understanding as being knowledge of causes etc. for the discussion of his cases and argue that it is implausible how subjects should gain the understanding Lipton attributes to them without explanation.

#### 3.2.1 Causation

The first example presented by Lipton is causation. He identifies causal information as a form of understanding. Many explanations provide this kind of understanding, but Lipton wants to investigate whether it is possible to gain causal information without an explanation involved.

We need cases that, in addition to not being explanations themselves, do not work by means of generating explanations that are then the proximate cause of the consequent understanding. […] [In such cases,] the process of acquiring understanding does not begin with an explanation, but the understanding is nevertheless a product of an explanation, which is not what we are looking for here.13

12 See Lipton, P. (2009), "Understanding without explanation." In de Regt, H. W., Leonelli, S. & Eigner, K. (eds.), *Scientific Understanding: Philosophical Perspectives*, pp. 43–63, Pittsburgh, University of Pittsburgh Press, pp.43f.

13 Ibid. pp. 44f.

Lipton works with the premise that there is something like tacit understanding, but nothing like a tacit explanation.This assumption enables him toidentify cases where causal information, alias understanding, can be achieved without the influence of any explanation. This happens via the use of images and physical models. Persons may grasp causal information that are provided by these devices, they may achieve genuine understanding, without being able to express an explanation that contains this information. Manipulation, in Lipton's view, is an even stronger example of understanding without explanation. A scientist may be an expert in using a complicated machinery because he acquired the relevant causal information, but he may not be able to explain this information to others. In sum, Lipton wants to be able to differentiate between someone who simply knows that a phenomenon occurs and someone who has a deep understanding of the causes of the phenomenon, butmight not be able to verbalize the causal information. He also mentions a possible critique to this idea, namely that a person may at least be able to say something about the causes of a phenomenon, even if some causal information remains tacit, i.e. cannot be made explicit. In such a case, Lipton maintains, the person would be able to provide an explanation, but this explanation would not exhaust the understanding of the person. Therefore, parts of the understanding of the person still do not require explanation.14

I fail to see how understanding can be attributed in these cases, and also how understanding conceptualized in this way should be valuable for science. I will first address the case of images and models, second the case of manipulation, and finally Lipton's general point about the natures of understanding as being tacit and explanation as being verbal or explicit.

Images and models are created to convey information, to make certain features salient that might otherwise be hidden in the real phenomenon. But this information does not automatically pass on to the person. Every representation requires interpretation by the subject. Just by looking at a representation and not interpreting *what* is represented and *how* it is represented, the image or model will not provide understanding of the represented phenomenon for the subject. The user makes the image or model intelligible to herself only by interpreting the representation, interpretation is a crucial part of representation.15 Interpretation requires some kind of reasoning about the object that is interpreted and relations of the object must be recognized. A user makes sense of the representation, recognizes the (causal) information captured in the model, by interpreting the model or image. And if some

14 See ibid. pp. 44ff.

15 The importance of interpretation is stressed in several philosophical accounts of representation, see for example Frigg, R. & Nguyen, J., "Scientific Representation", *The Stanford Encyclopedia of Philosophy* (Spring 2020 Edition), Edward N. Zalta (ed.), URL = https://plato.stanford. edu/archives/spr2020/entries/scientific-representation/ (last accessed April 12th, 2022).

causal information is represented, this relation will have to be recognized by the user and (correctly) interpreted. She must (correctly) identify what is the cause and what is the caused event shown in a representation. If the user achieves this, she will have a causal explanation of the represented phenomenon in her mind. For example, if a person sees an orrery, she will only gain understanding of planetary motion if she, first, identifies the model as a representation of the solar system (and not of an atomic nucleus orbited by electrons, for instance), and second, identifies the relations between parts of the representation. While parts of the process of interpretation might be tacit, I do not see how interpretation of representations is possible at all without recourse to some explicit conceptions that the person possesses. I engage with the relation of propositional or explicit knowledge and tacit knowledge or knowing-how in detail in sections 4.2 and 4.3. Additionally, it is not necessary that different people are able to give explanations that capture the same, or all, information. Representations can be good or bad, adequate or inadequate for certain purposes in certain contexts. People with different background knowledge might interpret a representation differently, their understanding of the representation might vary, but all of them would have gained some understanding, some causal knowledge, nevertheless.

I agree with Lipton that images and models provide information. But in the case of understanding, this information is not merely tacitly or unconsciously adopted and stored by the user. The information of a representation recognized by the user is consciously interpreted by her. If the user is not able to generate an explanation from an image or model, she has no understanding. Accordingly, she has not gained understanding without explanation, but she has rather not understood anything through the image or model, since she could not interpret the representation in light of her background knowledge. Lipton mentions the case of someone who "never *properly* understood the why of retrograde motion until [she] saw it demonstrated visually in a planetarium."16 But this example implies that the subject knew about retrograde motion *before* she saw the visual representation and already possessed information about the planets apparently moving into an opposite direction, maybe even an explanation of retrogrademotion, but she did not really understand the phenomenon merely on that basis. This is not the same as understanding retrograde motion by seeing it visually in a planetarium *without* having any explicit knowledge about it. And if the understanding provided by the model of retrograde motion is tacit understanding that cannot be made explicit, as Lipton argues, how would the person or anyone else be able to judge or to know that her understanding improved or is proper after seeing the visual model? Understanding the cause or an aspect of a phenomenon *properly* implies that the cause or aspect of the phenomenon must

16 Lipton (2009), p. 45, my emphasis.

be understood in a certain, proper, manner through a representation. If the understanding cannot be made explicit at all, it will not be possible to determine whether the person in question acquired a proper understanding, an inappropriate understanding, or maybe even no understanding at all, since tacit understanding is inaccessible for any subject, including the subjects that gained this understanding. If a person wants to make sure that she gained some understanding (causal knowledge) about a phenomenon by looking at a visual representation, she will have to make explicit what she understood.

Furthermore, according to my generic conception of explanation, which states that an explanation is a representation of relations of (parts of) the phenomenon under investigation, which provides reasons (an explanans) for features of (parts of) the phenomenon (the explanandum), images and physical models, the representations Lipton mentions, can be viewed as being explanations *themselves*. I do not restrict my conception of explanation to propositions.The same information concerning aspects of phenomena and their reasons can be captured in form of a proposition, an image, or a physical model, at least in many cases. Lipton apparently does not include images or physical models into his conception of explanation. I grant Lipton that models or images, in case they are not considered to be explanations themselves, can enable genuine understanding that is not possible by merely knowing a propositional explanation. This is a good point for arguing in favor of a genuine difference between knowledge of an explanation and understanding, but he does not show that understanding merely through visual representation and *without an (explicit) explanation at all* is possible.The visual representation of retrograde motion *alone* will not have provided understanding for the subject, since she would not have been able to make any sense of the representation without already knowing what is represented, and hence being able to identify the explanandum, the explanans, and their relation in this case.17

17 Victor Gijsbers is also not convinced by Lipton's example of images and models and his criticism is quite similar to mine. "Evidently, simply *seeing that* the planets perform a retrograde motion is not enough to count as understanding—if it did, we would not even need the planetarium, but could just look at the night sky. What more is needed? Well, we should be able to identify the salient features of the system, the features that determine that retrograde motion occurs. […] Anyone who hasn't grasped that the fact that the earth's shorter sidereal period is essential to the appearing of retrograde motion, has not understood why the phenomenon occurs. But anyone who has grasped this possesses an explanation of apparent retrograde motion. If the person were not able to express this explanation to others, perhaps because of a lack of useful vocabulary or linguistic skills in general, it would be pedantry to say that he understands but cannot explain. Even if he cannot express it, he does have an explanation." Gijsbers, V. (2013), "Understanding, explanation, and unification." *Studies in the History and Philosophy of Science*, 44, pp. 516–522, DOI: 10.1016/j.shpsa.2012.12.003, p. 518, original emphasis.