Interactionism (philosophy of mind)

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Interactionism or interactionist dualism is the theory in the philosophy of mind which holds that matter and mind are two distinct and independent substances that exert causal effects on one another. [1] It is one type of dualism, traditionally a type of substance dualism though more recently also sometimes a form of property dualism.

Philosophy of mind branch of philosophy on the nature of the mind


Substance theory, or substance–attribute theory, is an ontological theory about objecthood positing that a substance is distinct from its properties. A thing-in-itself is a property-bearer that must be distinguished from the properties it bears.

Property dualism philosophical theory (there is only 1 kind of substance in reality (matter),but that substance has 2 types of properties, material and mental);view that non-physical, mental properties (beliefs,desires,emotions) inhere in physical substances (brains)

Property dualism describes a category of positions in the philosophy of mind which hold that, although the world is composed of just one kind of substance—the physical kind—there exist two distinct kinds of properties: physical properties and mental properties. In other words, it is the view that non-physical, mental properties inhere in or supervene upon certain physical substances. As a doctrine, 'property dualism' is epistemic, as distinct from ontic.



Rene Descartes's illustration of dualism. Inputs are passed on by the sensory organs to the epiphysis in the brain and from there to the immaterial spirit. Descartes mind and body.gif

Interactionism was propounded by the French rationalist philosopher René Descartes (1596–1650), and continues to be associated with him. Descartes posited that the body, being physical matter, was characterized by spatial extension but not by thought and feeling, while the mind, being a separate substance, had no spatial extension but could think and feel. [2] Nevertheless, he maintained that the two interacted with one another, suggesting that this interaction occurred in the pineal gland of the brain. [3]

In philosophy, rationalism is the epistemological view that "regards reason as the chief source and test of knowledge" or "any view appealing to reason as a source of knowledge or justification". More formally, rationalism is defined as a methodology or a theory "in which the criterion of the truth is not sensory but intellectual and deductive".

René Descartes 17th-century French philosopher, mathematician, and scientist

René Descartes was a French philosopher, mathematician, and scientist. A native of the Kingdom of France, he spent about 20 years (1629–1649) of his life in the Dutch Republic after serving for a while in the Dutch States Army of Maurice of Nassau, Prince of Orange and the Stadtholder of the United Provinces. He is generally considered one of the most notable intellectual figures of the Dutch Golden Age.

Pineal gland small endocrine gland found in most vertebrates, which produces melatonin; in humans, located in the epithalamus, in a groove where the two halves of the thalamus join; its shape and size resembles a pine nut, after which it is named

The pineal gland, conarium, or epiphysis cerebri, is a small endocrine gland in the brain of most vertebrates. The pineal gland produces melatonin, a serotonin-derived hormone which modulates sleep patterns in both circadian and seasonal cycles. The shape of the gland resembles a pine cone from which it derived its name. The pineal gland is located in the epithalamus, near the center of the brain, between the two hemispheres, tucked in a groove where the two halves of the thalamus join.. The pineal gland is one of the neuroendocrine secretory circumventricular organs that are not part of the blood-brain-barrier.

In the 20th century, its most significant defenders have been the noted philosopher of science Karl Popper and the neurophysiologist John Carew Eccles. [4] Popper in fact divided reality into three "worlds"—the physical, the mental, and objective knowledge (outside the mind)—all of which interact, [5] and Eccles adopted this same "trialist" form of interactionism. [6] Other notable recent philosophers to take an interactionist stance have been Richard Swinburne, John Foster, David Hodgson, and Wilfrid Sellars, in addition to the physicist Henry Stapp. [7]

Karl Popper Austrian-British philosopher of science

Sir Karl Raimund Popper was an Austrian-British philosopher and professor.

Popper's three worlds is a way of looking at reality, described by the British philosopher Karl Popper in a lecture in 1978. The concept involves three interacting worlds, called World 1, World 2 and World 3.

Richard Swinburne British philosopher of religion

Richard G. Swinburne is a British philosopher. He is an Emeritus Professor of Philosophy at the University of Oxford. Over the last 50 years Swinburne has been an influential proponent of philosophical arguments for the existence of God. His philosophical contributions are primarily in the philosophy of religion and philosophy of science. He aroused much discussion with his early work in the philosophy of religion, a trilogy of books consisting of The Coherence of Theism, The Existence of God, and Faith and Reason.

In his 1996 book The Conscious Mind , David Chalmers rejected interactionism, but in 2002 he reversed his position and listed it along with epiphenomenalism and what he calls "Type-F monism" as a position worth examining. Rather than invoking two distinct substances, he defines interactionism as the view that "microphysics is not causally closed, and that phenomenal properties play a causal role in affecting the physical world." (See property dualism.) He argues the most plausible place for consciousness to impact physics is the collapse of the wave function in quantum mechanics. [7]

<i>The Conscious Mind</i> philosophy book by David Chalmers

The Conscious Mind: In Search of a Fundamental Theory is a 1996 book by David Chalmers, an Australian philosopher specializing in the area of philosophy of mind.

David Chalmers Australian philosopher and cognitive scientist

David John Chalmers is an Australian philosopher and cognitive scientist specializing in the areas of philosophy of mind and philosophy of language. He is Professor of Philosophy and Director of the Centre for Consciousness at the Australian National University. He is also a University Professor, Professor of Philosophy and Neural Science, and a Director of the Center for Mind, Brain and Consciousness at New York University. In 2013, he was elected a Fellow of the American Academy of Arts & Sciences.

Epiphenomenalism is a position on the mind–body problem which holds that physical and biochemical events within the human body are causal with respect to mental events. According to this view, subjective mental events are completely dependent for their existence on corresponding physical and biochemical events within the human body and themselves have no causal efficacy on physical events. The appearance that subjective mental states influence physical events is merely an illusion. For instance, fear seems to make the heart beat faster, but according to epiphenomenalism the biochemical secretions of the brain and nervous system —not the experience of fear—is what raises the heartbeat. Because mental events are a kind of overflow that cannot cause anything physical, yet have non-physical properties, epiphenomenalism is viewed as a form of property dualism.

The New Catholic Encyclopedia argues that a non-physical mind and mind-body interaction follow necessarily from the Catholic doctrines of the soul and free will. [8]

The New Catholic Encyclopedia (NCE) is a multi-volume reference work on Roman Catholic history and belief edited by the faculty of The Catholic University of America. It was intended by the faculty to become, like its predecessor the 1914 Catholic Encyclopedia, a standard reference work for students, teachers, librarians, journalists, and general readers interested in the history, doctrine, practices, and people of the Catholic faith. However, unlike its predecessor, its first edition also contained more general articles on science, education, and the liberal arts. The NCE was originally published by McGraw-Hill in 1967. A second edition, which gave up the articles more reminiscent of a general encyclopedia, was published in 2002 and was listed as one of Library Journal's "Best Reference Sources" for 2003.

Catholic Church Christian church led by the Bishop of Rome


Soul essence of an individual



Problem of causal interaction

One objection often posed to interactionism is the problem of causal interaction – how the two different substances the theory posits, the mental and the physical, can exert an impact on one another. Descartes' theory that interaction between the mind and the physical world occurred in the pineal gland was seen as inadequate by a number of philosophers in his era, who offered alternate views: Nicholas Malebranche suggested occasionalism, according to which mind and body appear to interact but are in fact moved separately by God, while Gottfried Leibniz argued in The Monadology that mind and body are in a pre-established harmony. [3] On the other hand, Baruch Spinoza rejected Descartes' dualism and proposed that mind and matter were in fact properties of a single substance, [3] thereby prefiguring the modern perspective of neutral monism.

Occasionalism is a philosophical theory about causation which says that created substances cannot be efficient causes of events. Instead, all events are taken to be caused directly by God. The theory states that the illusion of efficient causation between mundane events arises out of God's causing of one event after another. However, there is no necessary connection between the two: it is not that the first event causes God to cause the second event: rather, God first causes one and then causes the other.

The Monadology is one of Gottfried Leibniz's best known works representing his later philosophy. It is a short text which sketches in some 90 paragraphs a metaphysics of simple substances, or monads.

Gottfried Leibniz's theory of pre-established harmony is a philosophical theory about causation under which every "substance" affects only itself, but all the substances in the world nevertheless seem to causally interact with each other because they have been programmed by God in advance to "harmonize" with each other. Leibniz's term for these substances was "monads" which he described in a popular work as "windowless".

Today the problem of causal interaction is frequently viewed as a conclusive argument against interactionism. [9] On the other hand, it has been suggested that given many disciplines deal with things they do not entirely understand, dualists not entirely understanding the mechanism of mind-body interaction need not be seen as definitive refutation. [9] The idea that causation necessarily depends on push-pull mechanisms (which would not be possible for a substance that did not occupy space) is also arguably based on obsolete conceptions of physics. [2]

The problem of mental causation is also discussed in the context of other positions on the mind-body problem, such as property dualism and anomalous monism. [2]

Compatibility with the conservation of energy

A more recent related objection is the argument from physics, which argues that a mental substance impacting the physical world would contradict principles of physics. [1] In particular, if some external source of energy is responsible for the interactions, it would violate the law of conservation of energy. [10] Two main responses to this have been to suggest the mind influences the distribution but not the quantity of energy in the brain and to deny that the brain is a causally closed system in which conservation of energy would apply. [1] [8]

Causal closure

Taking the argument a step further, it has been argued that because physics fully accounts for the causes of all physical movements, there can be no place for the a non-physical mind to play a role. [2] The principle, in slightly different iterations, has variously been called causal closure, completeness of the physical, physical closure, and physical comprehensiveness. [2] This has been the foremost argument against interactionism in contemporary philosophy. [7]

Some philosophers have suggested the influence of the mind on the body could be reconciled with deterministic physical laws by proposing the mind's impacts instead take place at points of quantum indeterminacy. [9] Karl Popper and John Eccles, as well as the physicist Henry Stapp, have theorized that such indeterminacy may apply at the macroscopic scale. [4] (See quantum mind.) However, Max Tegmark has argued that classical and quantum calculations show that quantum decoherence effects do not play a role in brain activity. [11] David Chalmers has noted (without necessarily endorsing) a second possibility within quantum mechanics, that consciousness' causal role is to collapse the wave function as per the Von Neumann-Wigner interpretation of quantum mechanics. [12] He acknowledges this is at odds with the interpretations of quantum mechanics held by most physicists, but notes, "There is some irony in the fact that philosophers reject interactionism on largely physical grounds (it is incompatible with physical theory), while physicists reject an interactionist interpretation of quantum mechanics on largely philosophical grounds (it is dualistic). Taken conjointly, these reasons carry little force...". [7]

There remains a literature in philosophy and science, albeit a much-contested one, that asserts evidence for emergence in various domains, which would undermine the principle of causal closure. [2] (See emergentism.) Another option that has been suggested is that the interaction may involve dark energy, dark matter or some other currently unknown scientific process. [13]

Another possible resolution is akin to parallelism—Eugene Mills holds that behavioral events are causally overdetermined, and can be explained by either physical or mental causes alone. [14] An overdetermined event is fully accounted for by multiple causes at once. [15] However, J. J. C. Smart and Paul Churchland have argued that if physical phenomena fully determine behavioral events, then by Occam's razor a non-physical mind is unnecessary. [16] Andrew Melnyk argues that overdetermination would require an "intolerable coincidence." [2]

While causal closure remains a key obstacle for interactionism, it is not relevant to all forms of dualism; epiphenomenalism and parallelism are unaffected as they do not posit that the mind affects the body. [2]

Relationship to other positions

Four varieties of dualist causal interaction. The arrows indicate the direction of causations. Mental and physical states are shown in red and blue, respectively. DualismCausationViews3.svg

Interactionism can be distinguished from competing dualist theories of causation, including epiphenomenalism (which admits causation, but views causation as unidirectional rather than bidirectional), and parallelism (which denies causation, while seeking to explain the semblance of causation by other means such as pre-established harmony or occasionalism). [1]

In The Conscious Mind, David Chalmers argued that regardless of the mechanism by which the mental might impact the physical if interactionism were true, there was a deeper conceptual issue: the chosen mechanism could always be separated from its phenomenal component, leading to simply a new form of epiphenomenalism. [12] Later, he suggested that while the causal component could be separated, interactionism was like "type-F monism" (Russellian monism, panpsychism, and panprotopsychism) in that it gave entities externally characterized by physical relationships the additional intrinsic feature of conscious properties. [7]

See also

Related Research Articles

Mind combination of cognitive faculties that provides consciousness, thinking, reasoning, perception, and judgement in humans and potentially other life forms

The mind is a set of cognitive faculties including consciousness, imagination, perception, thinking, judgement, language and memory. It is usually defined as the faculty of an entity's thoughts and consciousness. It holds the power of imagination, recognition, and appreciation, and is responsible for processing feelings and emotions, resulting in attitudes and actions.

In philosophy, physicalism is the metaphysical thesis that "everything is physical", that there is "nothing over and above" the physical, or that everything supervenes on the physical. Physicalism is a form of ontological monism—a "one substance" view of the nature of reality as opposed to a "two-substance" (dualism) or "many-substance" (pluralism) view. Both the definition of "physical" and the meaning of physicalism have been debated.

Mind–body dualism philosophical theory that mental phenomena are non-physical and that matter exists independently of mind

Mind–body dualism, or mind–body duality, is a view in the philosophy of mind that mental phenomena are, in some respects, non-physical, or that the mind and body are distinct and separable. Thus, it encompasses a set of views about the relationship between mind and matter, and between subject and object, and is contrasted with other positions, such as physicalism and enactivism, in the mind–body problem.

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Mental substance idea held by dualists and idealists, that minds are made-up of non-physical substance



In philosophy, panpsychism is the view that consciousness, mind, or soul (psyche) is a universal and primordial feature of all things. Panpsychists see themselves as minds in a world of mind.

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Jaegwon Kim is a Korean-American philosopher who is now an emeritus professor at Brown University, but who also taught at several other leading American universities. He is best known for his work on mental causation, the mind-body problem and the metaphysics of supervenience and events. Key themes in his work include: a rejection of Cartesian metaphysics, the limitations of strict psychophysical identity, supervenience, and the individuation of events. Kim's work on these and other contemporary metaphysical and epistemological issues is well represented by the papers collected in Supervenience and Mind: Selected Philosophical Essays (1993).

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In the philosophy of mind, psychophysical parallelism is the theory that mental and bodily events are perfectly coordinated, without any causal interaction between them. As such, it affirms the correlation of mental and bodily events, but denies a direct cause and effect relation between mind and body. This coordination of mental and bodily events has been postulated to occur either in advance or at the time of the event. On this view, mental and bodily phenomena are independent but yet inseparable, like two sides of a coin.

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Mind in eastern philosophy branch of philosophy on the nature of the mind

The study of the mind in Eastern philosophy has parallels to the Western study of the Philosophy of mind as a branch of philosophy that studies the nature of the mind. Dualism and monism are the two central schools of thought on the mind–body problem in the Western tradition, although nuanced views have arisen that do not fit one or the other category neatly. Dualism is found in both Eastern and Western traditions but its entry into Western philosophy was thanks to René Descartes in the 17th century. This article on mind in eastern philosophy deals with this subject from the standpoint of eastern philosophy which is historically strongly separated from the Western tradition and its approach to the Western philosophy of mind.


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