- Key People:
- Aristotle
- Plato
- St. Augustine
- John Locke
- Immanuel Kant
- Related Topics:
- shabdadvaita
- agnoiology
- justification
- perspectivism
- theory of appearing
- On the Web:
- Routledge Encyclopedia of Philosophy - Epistemology (Oct. 16, 2026)
Epistemology
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What is epistemology?
Epistemology, also referred to as the theory of knowledge, is the branch of philosophy that studies the "nature, origin, and limits of human knowledge". It explores how we investigate concepts, examining the use of knowledge and related expressions in everyday language to gain insight into the concepts associated with them.
Epistemology addresses questions, such as what can be known, how knowledge is acquired, and what differentiates knowledge from belief. Contemporary epistemology is characterized by Continental and analytic approaches. The Continental approach focuses on overcoming the gap between the knower and the known, while the analytic approach emphasizes language's role in philosophical problems.
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Why is epistemology important in philosophy?
Epistemology, the study of knowledge, is one of philosophy's primary branches, alongside metaphysics, logic, and ethics. Throughout its history, epistemology has sought to describe features of the world, like the contents of the human mind, and to determine what mental content should be considered knowledge.
Epistemology also has a justificatory function, asking what beliefs can be rationally justified and what one ought to believe. Evolutionary epistemology studies the origins of human knowledge and the adaptive significance of cognitive faculties. Contemporary philosophy has focused on the gap between the knower and the known. It also challenges the notion that knowledge is primarily theoretical.
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What do philosophers mean by 'knowledge'?
In epistemology, the philosophical study of knowledge, philosophers have long debated the nature of knowledge. They treat the question as a conceptual one, investigating the concept through the use of "knowledge" and related expressions in everyday language.
Since the time of Plato, knowledge has been defined as justified true belief, though disagreements persist about the nature of justification. John Locke defined knowledge as the perception of the connection and agreement or disagreement and repugnancy of any of our ideas.
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What are the main ways people can gain knowledge?
Epistemology, the study of knowledge, identifies several main ways people gain knowledge.
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Rationalism asserts reason is the primary source of knowledge. It emphasizes a priori knowledge gained through intellectual insight, independent of sense experience.
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Empiricism emphasizes experience as the source of knowledge, where significant propositions are known through sensory experience. Even though empiricists acknowledge a priori knowledge, they deny its significance.
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Intuition refers to immediate apprehension or understanding without conscious reasoning or observation. It is considered an original source of knowledge that cannot be acquired by inference, observation, reason, or experience.
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What is the difference between belief and knowledge?
In epistemology, belief is a mental attitude of accepting a proposition without full intellectual knowledge that guarantees its truth. Beliefs can range from suspicion to conviction. Knowledge, traditionally defined, is a justified, true belief.
However, knowledge requires truth, meaning one cannot "know" something false. Knowledge also requires justification, which is a good reason or evidence supporting the belief. Belief becomes knowledge when the truth of a proposition is evident to the believer. Some philosophers, however, deny that knowledge is a mental state.
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How do philosophers check if something is true knowledge or just an opinion?
In epistemology, philosophers seek to distinguish between true knowledge and mere opinion through rigorous examination and justification. Knowledge is defined as true belief with justification.
To determine if a belief qualifies as knowledge, philosophers employ several methods:
* Skepticism Skeptics question the possibility of acquiring knowledge, challenging claims and searching for counterexamples.
* Justification Philosophers ask what kinds of belief can be rationally justified. Plato argued that knowledge is justified true belief.
* Coherentism Truth is a feature of the overall body of belief considered as a system of logically interrelated components.
* Empiricism Empiricists believe that a sentence is meaningful only if it is either tautologous or in principle verifiable on the basis of sense experience.
* Pragmatism Pragmatists suggest that belief systems can be compared in pragmatic or utilitarian terms.3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Epistemology, the philosophical study of the nature, origin, and limits of human knowledge. The term is derived from the Greek epistēmē (“knowledge”) and logos (“reason”), and accordingly the field is sometimes referred to as the theory of knowledge. Epistemology has a long history within Western philosophy, beginning with the ancient Greeks and continuing to the present. Along with metaphysics, logic, and ethics, it is one of the four main branches of philosophy, and nearly every great philosopher has contributed to it.
The nature of epistemology
Epistemology as a discipline
Why should there be a discipline such as epistemology? Aristotle (384–322 bce) provided the answer when he said that philosophy begins in a kind of wonder or puzzlement. Nearly all human beings wish to comprehend the world they live in, and many of them construct theories of various kinds to help them make sense of it. Because many aspects of the world defy easy explanation, however, most people are likely to cease their efforts at some point and to content themselves with whatever degree of understanding they have managed to achieve.
Unlike most people, philosophers are captivated—some would say obsessed—by the idea of understanding the world in the most general terms possible. Accordingly, they attempt to construct theories that are synoptic, descriptively accurate, explanatorily powerful, and in all other respects rationally defensible. In doing so, they carry the process of inquiry further than other people tend to do, and this is what is meant by saying that they develop a philosophy about such matters.
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Like most people, epistemologists often begin their speculations with the assumption that they have a great deal of knowledge. As they reflect upon what they presumably know, however, they discover that it is much less secure than they realized, and indeed they come to think that many of what had been their firmest beliefs are dubious or even false. Such doubts arise from certain anomalies in people’s experience of the world. Two of those anomalies will be described in detail here in order to illustrate how they call into question common claims to knowledge about the world.
Two epistemological problems
Knowledge of the external world
Most people have noticed that vision can play tricks. A straight stick submerged in water looks bent, though it is not; railroad tracks seem to converge in the distance, but they do not; and a page of English-language print reflected in a mirror cannot be read from left to right, though in all other circumstances it can. Each of those phenomena is misleading in some way. Anyone who believes that the stick is bent, that the railroad tracks converge, and so on is mistaken about how the world really is.
Although such anomalies may seem simple and unproblematic at first, deeper consideration of them shows that just the opposite is true. How does one know that the stick is not really bent and that the tracks do not really converge? Suppose one says that one knows that the stick is not really bent because when it is removed from the water, one can see that it is straight. But does seeing a straight stick out of water provide a good reason for thinking that when it is in water, it is not bent? Suppose one says that the tracks do not really converge because the train passes over them at the point where they seem to converge. But how does one know that the wheels on the train do not converge at that point also? What justifies preferring some of those beliefs to others, especially when all of them are based upon what is seen? What one sees is that the stick in water is bent and that the stick out of water is straight. Why, then, is the stick declared really to be straight? Why, in effect, is priority given to one perception over another?
One possible answer is to say that vision is not sufficient to give knowledge of how things are. Vision needs to be “corrected” with information derived from the other senses. Suppose then that a person asserts that a good reason for believing that the stick in water is straight is that when the stick is in water, one can feel with one’s hands that it is straight. But what justifies the belief that the sense of touch is more reliable than vision? After all, touch gives rise to misperceptions just as vision does. For example, if a person chills one hand and warms the other and then puts both in a tub of lukewarm water, the water will feel warm to the cold hand and cold to the warm hand. Thus, the difficulty cannot be resolved by appealing to input from the other senses.
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Another possible response would begin by granting that none of the senses is guaranteed to present things as they really are. The belief that the stick is really straight, therefore, must be justified on the basis of some other form of awareness, perhaps reason. But why should reason be accepted as infallible? It is often used imperfectly, as when one forgets, miscalculates, or jumps to conclusions. Moreover, why should one trust reason if its conclusions run counter to those derived from sensation, considering that sense experience is obviously the basis of much of what is known about the world?
Clearly, there is a network of difficulties here, and one will have to think hard in order to arrive at a compelling defense of the apparently simple claim that the stick is truly straight. A person who accepts this challenge will, in effect, be addressing the larger philosophical problem of knowledge of the external world. That problem consists of two issues: how one can know whether there is a reality that exists independently of sense experience, given that sense experience is ultimately the only evidence one has for the existence of anything; and how one can know what anything is really like, given that different kinds of sensory evidence often conflict with each other.