section_path: History
section_name: History
paragraph_text: History
  
  Early reflections on the nature and sources of knowledge are found in ancient history. In ancient Greek philosophy, Plato (427–347 BCE) studied what knowledge is, examining how it differs from true opinion by being based on good reasons. According to him, the process of learning something is a form of recollection in which the soul remembers what it already knew before. Aristotle (384–322 BCE) was particularly interested in scientific knowledge, exploring the role of sensory experience and how to make inferences from general principles. The Hellenistic schools began to arise in the 4th century BCE. The Epicureans had an empiricist outlook, stating that sensations are always accurate and act as the supreme standard of judgments. The Stoics defended a similar position but limited themselves to lucid and specific sensations, which they regarded as true. The skepticists questioned that knowledge is possible, recommending instead suspension of judgment to arrive at a state of tranquility.
  
  The Upanishads, philosophical scriptures composed in ancient India between 700 and 300 BCE, examined how people acquire knowledge, including the role of introspection, comparison, and deduction. In the 6th century BCE, the school of Ajñana developed a radical skepticism questioning the possibility and usefulness of knowledge. The school of Nyaya emerged in the 2nd century BCE and provided a systematic treatment of how people acquire knowledge, distinguishing between valid and invalid sources. When Buddhist philosophers later became interested in epistemology, they relied on concepts developed in Nyaya and other traditions. Buddhist philosopher Dharmakirti (6th or 7th century CE) analyzed the process of knowing as a series of causally related events.
  
  Ancient Chinese philosophers understood knowledge as an interconnected phenomenon fundamentally linked to ethical behavior and social involvement. Many saw wisdom as the goal of attaining knowledge. Mozi (470–391 BCE) proposed a pragmatic approach to knowledge using historical records, sensory evidence, and practical outcomes to validate beliefs. Mencius (c. 372–289 BCE) explored analogical reasoning as another source of knowledge. Xunzi (c. 310-220 BCE) aimed to combine empirical observation and rational inquiry. He emphasized the importance of clarity and standards of reasoning without excluding the role of feeling and emotion.
  
  The relation between reason and faith was a central topic in the medieval period. In Arabic–Persian philosophy, al-Farabi (c. 870–950) and Averroes (1126–1198) discussed how philosophy and theology interact and which is the better vehicle to truth. Al-Ghazali (c. 1056–1111) criticized many of the core teachings of previous Islamic philosophers, saying that they rely on unproven assumptions that do not amount to knowledge. In Western philosophy, Anselm of Canterbury (1033–1109) proposed that theological teaching and philosophical inquiry are in harmony and complement each other. Peter Abelard (1079–1142) argued against unquestioned theological authorities and said that all things are open to rational doubt. Influenced by Aristotle, Thomas Aquinas (1225–1274) developed an empiricist theory, stating that "nothing is in the intellect unless it first appeared in the senses". According to an early form of direct realism proposed by William of Ockham (c. 1285–1349), perception of mind-independent objects happens directly without intermediaries. Meanwhile, in 14th-century India, Gaṅgeśa developed a reliabilist theory of knowledge and considered the problems of testimony and fallacies. In China, Wang Yangming (1472–1529) explored the unity of knowledge and action, holding that moral knowledge is inborn and can be attained by overcoming self-interest.
  
  The course of modern philosophy was shaped by René Descartes (1596–1650), who claimed that philosophy must begin from a position of indubitable knowledge of first principles. Inspired by skepticism, he aimed to find absolutely certain knowledge by encountering truths that cannot be doubted. He thought that this is the case for the assertion " I think, therefore I am ", from which he constructed the rest of his philosophical system. Descartes, together with Baruch Spinoza (1632–1677) and Gottfried Wilhelm Leibniz (1646–1716), belonged to the school of rationalism, which asserts that the mind possesses innate ideas independent of experience. John Locke (1632–1704) rejected this view in favor of an empiricism according to which the mind is a blank slate. This means that all ideas depend on sense experience, either as "ideas of sense", which are directly presented through the senses, or as "ideas of reflection", which the mind creates by reflecting on ideas of sense. David Hume (1711–1776) used this idea to explore the limits of what people can know. He said that knowledge of facts is never certain, adding that knowledge of relations between ideas, like mathematical truths, can be certain but contains no information about the world. Immanuel Kant (1724–1804) tried to find a middle position between rationalism and empiricism by identifying a type of knowledge that Hume had missed. For Kant, this is knowledge about principles that underlie all experience and structure it, such as spatial and temporal relations and fundamental categories of understanding.
  
  In the 19th-century, Georg Wilhelm Friedrich Hegel (1770–1831) argued against empiricism, saying that sensory impressions on their own cannot amount to knowledge since all knowledge is actively structured by the knowing subject. John Stuart Mill (1806–1873) defended a wide-sweeping form of empiricism and explained knowledge of general truths through inductive reasoning. Charles Peirce (1839–1914) thought that all knowledge is fallible, emphasizing that knowledge seekers should always be ready to revise their beliefs if new evidence is encountered. He used this idea to argue against Cartesian foundationalism seeking absolutely certain truths.
  
  In the 20th century, fallibilism was further explored by J. L. Austin (1911–1960) and Karl Popper (1902–1994). In continental philosophy, Edmund Husserl (1859–1938) applied the skeptic idea of suspending judgment to the study of experience. By not judging whether an experience is accurate or not, he tried to describe the internal structure of experience instead. Logical positivists, like A. J. Ayer (1910–1989), said that all knowledge is either empirical or analytic. Bertrand Russell (1872–1970) developed an empiricist sense-datum theory, distinguishing between direct knowledge by acquaintance of sense data and indirect knowledge by description, which is inferred from knowledge by acquaintance. Common sense had a central place in G. E. Moore 's (1873–1958) epistemology. He used trivial observations, like the fact that he has two hands, to argue against abstract philosophical theories that deviate from common sense. Ordinary language philosophy, as practiced by the late Ludwig Wittgenstein (1889–1951), is a similar approach that tries to extract epistemological insights from how ordinary language is used.
  
  Edmund Gettier (1927–2021) conceived counterexamples against the idea that knowledge is the same as justified true belief. These counterexamples prompted many philosophers to suggest alternative definitions of knowledge. One of the alternatives considered was reliabilism, which says that knowledge requires reliable sources, shifting the focus away from justification. Virtue epistemology, a closely related response, analyses belief formation in terms of the intellectual virtues or cognitive competencies involved in the process. Naturalized epistemology, as conceived by Willard Van Orman Quine (1908–2000), employs concepts and ideas from the natural sciences to formulate its theories. Other developments in late 20th-century epistemology were the emergence of social, feminist, and historical epistemology.