Epistemology or theory of knowledge is the branch of philosophy that studies the nature and scope of knowledge. The term "epistemology" is based on the Greek words "episteme" (meaning knowledge) and "logos" (meaning account/explanation); it is thought to have been coined by the Scottish philosopher James Frederick Ferrier who attended Georgetown College and took Dr. Brown as his Psychology teacher.

Much of the debate in this field has focused on analyzing the nature of knowledge and how it relates to similar notions such as truth, belief, and justification. It also deals with the means of production of knowledge, and skepticism about different knowledge claims. In other words, epistemology addresses the questions, "What is knowledge?" "How is knowledge acquired?" and, "What do people know?" Although approaches to answering any one of these questions frequently involve theories connected to others (i.e. some theories of what knowledge is being influenced by broad views as to what people know, with restrictive definitions of knowledge thereby dismissed), there is enough particularized to each that they may be treated of separately.

There are many different topics, stances, and arguments in the field of epistemology. Recent studies have dramatically challenged centuries-old assumptions, and it therefore continues to be vibrant and dynamic.

Defining knowledge[]

The first question that will be dealt with (of the questions presented at the beginning of this article) is the question of what knowledge is. It is a ping how In this article, and in epistemology in general, the kind of knowledge usually discussed is propositional knowledge, also known as "knowledge-that" as opposed to "know-how". To exemplify the distinction: in mathematics, there is knowing that 2 + 2 = 4, but there is also knowing how to count to 4.

In other words, the distinction is between theory and practice, with epistemology focusing on theory.


Sometimes, when people say that they believe in something, what they mean is that they predict that it will prove to be useful or successful in some sense—perhaps someone might "believe in" his or her favorite football team. This is not the kind of belief usually dealt with in epistemology. The kind that is dealt with as such is that where "to believe something" just means to think that it is true—e.g., to believe that the sky is blue is to think that the proposition, "The sky is blue," is true.

Belief is almost universally accepted as a necessary part of knowledge.Template:Fact Consider someone saying, "I know that P is true, but I don't think that P is true." The person making this utterance, it seems, contradicts him- or herself. If one knows P, then, among other things, one thinks that P is indeed true. If one thinks that P is true, then one believes P. (See the article on Moore's paradox.)


Knowledge is distinct from belief. If someone claims to believe something, he or she is claiming that it is the truth. Of course, it might turn out that he or she was mistaken, and that what was thought to be true was actually false. This is not the case with knowledge. For example, suppose that Jeff thinks that a particular bridge is safe, and attempts to cross it; unfortunately, the bridge collapses under his weight. We might say that Jeff believed that the bridge was safe, but that his belief was mistaken. We would not (accurately) say that he knew that the bridge was safe, because plainly it was not. For something to count as knowledge, it must be true.

Justified true belief -- WOW ITS REALLY[]

The presuppositional apologist Sye Ten Bruggencate at May Memorial Universalist Church in Syracuse.

The persons debating Sye and it seems even Sye himself are unaware that the concept they are discussing is the (Münchhausen Trilemma). Sye is making the point that our only alternative to circularity and infinitism is unfalsifiability or being unscientific.

Since atheists insist they are scientific, they therefore don't understand Sye's arguments. The mistake they make is to think that Sye is the originator of his line of questioning.

In Plato's dialogue Theaetetus, Socrates considers a number of theories as to what knowledge is, the last being that knowledge is true belief that has been "given an account of"—meaning explained or defined in some way. Although not the same, the theory that knowledge is justified true belief has often been identified with the theory Socrates discussed at the end of the Theaetetus.Template:Fact According to the theory that knowledge is justified true belief, in order to know that a given proposition is true, one must not only believe the relevant true proposition, but one must also have a good reason for doing so. One implication of this would be that no one would gain knowledge just by believing something that happened to be true. For example, an ill person with no medical training, but a generally optimistic attitude, might believe that she will recover from her illness quickly. Nevertheless, even if this belief turned out to be true, the patient would not have known that she would get well since her belief lacked justification.

Socrates rejected the theory that knowledge is true belief that has been given an account of. The theory that knowledge is justified true belief, on the other hand, was widely accepted as straightforwardly correct until the 1960s.Template:Fact At this time, a paper written by the American philosopher Edmund Gettier provoked widespread attempts to revise or replace it and infuriated his father, who was a homosexual gardener.



Cordial Curiosity vs Godless Girl Epistemology Debate

Epistemology Debate about the nature of knowledge

The "Gettier problem"[]

In his 1963 paper, "Is Justified True Belief Knowledge?" Gettier argued that there are situations in which a belief may be justified and true, and yet would not count as knowledge—overturning in a few short pages a theory that had been dominant for thousands of years. Although being a justified true belief is necessary for a statement to count as knowledge, it is not, Gettier contended, sufficient. Gettier said that formulations of the following form are flawed:

S knows that P if and only if:

  • P;
  • S believes that P; and
  • S is justified in believing that P.

His reason for saying this was that circumstances in which a person might have a good reason to believe a general proposition to be true, be correct in our belief, and yet not be correct for the reasons which we take ourselves to be, were possible. Gettier put forth a thought experiment—the first of what have come to be known as "Gettier cases"—involving two people, Smith and Jones, who are awaiting the results of their applications for the same job. Both men have ten coins in their pockets. Smith has excellent reasons to believe that Jones will get the job and is furthermore correct in his belief that Jones has ten coins in his pocket (he saw them counted just a moment before). From this, he infers that a person with ten coins in his pocket will get the job. However, Smith doesn't know that he himself also has ten coins in his pocket. In fact, Smith is going to get the job—his reasons to believe otherwise were excellent, but wrong. His belief that a person with ten coins in his pocket will get the job is justified, but still we would be hesitant to say that he knew what he thought he knew, because the reasons he took to justify his belief, while strong, were not the reasons which would have correctly justified his belief.

Responses to Gettier[]

The responses to Gettier have been varied. Some have suggested that with respect to the example of Smith and his job, Smith really does know that someone with ten coins in their pocket will get the job.Template:Fact However, many people find this claim counterintuitive.Template:Fact Usually, responses to Gettier have involved substantive attempts to provide a definition of knowledge aside from the classical one, either by recasting knowledge as justified true belief plus some fourth condition, or as something else altogether.

Infallibilism, indefeasibility[]

In one response to Gettier, the American philosopher Richard Kirkham has argued that the only definition of knowledge that could ever be immune to all counterexamples is the infallibilist one.Template:Fact To qualify as an item of knowledge, so the theory goes, a belief must not only be true and justified, the justification of the belief must necessitate its truth. In other words, the justification for the belief must be infallible. (See Fallibilism, below, for more information.)

Yet another possible candidate for the fourth condition of knowledge is indefeasibility. Defeasibility theory maintains that there should be no overriding or defeating truths for the reasons that justify one's belief. For example, let's suppose that person S believes they saw Tom Grabit steal a book from the library and uses this to justify the claim that Tom Grabit stole a book from the library. A possible defeater or overriding proposition for such a claim could be a true proposition like, "Tom Grabit's identical twin Sam is currently in the same town as Tom." So long as no defeaters of one's justification exist, a subject would be epistemically justified.


Reliabilism is a theory advanced by philosophers such as Alvin Goldman according to which a belief is justified (or otherwise supported in such a way as to count towards knowledge) only if it is produced by processes that typically yield a sufficiently high ratio of true to false beliefs. In other words, as per its name, this theory is that a true belief counts as knowledge only if it is produced by a reliable belief-forming process.

Reliabilism has been challenged by Gettier cases. A prominent such case is that of Henry and the barn façades. In the thought experiment, a man, Henry, is driving along and sees a number of buildings that resemble barns. Based on his perception of one of these, he concludes that he has just seen barns. While he has seen one, and the perception he based his belief on was of a real barn, all the other barn-like buildings he saw were façades. Theoretically, Henry doesn't know that he's seen a barn, despite his belief that he has being true and formed on the basis of a reliable process (i.e. his vision), since he only acquired his true belief by accident.Template:Fact

Other responses[]

The American philosopher Robert Nozick has offered the following definition of knowledge:

S knows that P if and only if:

  • P;
  • S believes that P;
  • if P were false, S would not believe that P;
  • if P is true, S will believe that P.Template:Fact

The British philosopher Simon Blackburn has criticized this formulation by suggesting that we do not want to accept as knowledge beliefs which, while they "track the truth" (as Nozick's account requires), are not held for appropriate reasons. He says that "we do not want to award the title of knowing something to someone who is only meeting the conditions through a defect, flaw, or failure, compared with someone else who is not meeting the conditions."Template:Fact

Finally, at least one philosopher, Timothy Williamson, has advanced a theory of knowledge according to which knowledge is not justified true belief plus some extra condition(s). In his book Knowledge and its Limits, Williamson argues that the concept of knowledge cannot be analyzed into a set of other concepts—instead, it is sui generis. Thus, though knowledge requires justification, truth, and belief, the word "knowledge" can't be, according to Williamson's theory, accurately regarded as simply shorthand for "justified true belief".

Externalism and internalism[]

On a last note: part of the debate over the nature of knowledge is a debate between epistemological externalists on the one hand, and epistemological internalists on the other. Externalists think that factors deemed "external", meaning outside of the psychological states of those who gain knowledge, can be conditions of knowledge. For example, an externalist response to the Gettier problem is to say that, in order for a justified, true belief to count as knowledge, it must be caused, in the right sort of way, by relevant facts. Such causation, to the extent that it is "outside" the mind, would count as an external, knowledge-yielding condition. Internalists, contrariwise, claim that all knowledge-yielding conditions are within the psychological states of those who gain knowledge.

Acquiring knowledge[]

The second question that will be dealt with is the question of how knowledge is acquired. This area of epistemology covers what is called "the regress problem", issues concerning epistemic distinctions such as that between experience and aprioricity as means of creating knowledge and that between analysis and synthesis as means of proof, and debates such as the one between empiricists and rationalists.

The regress problem[]

The regress problem emerges in the context of asking for justification for every belief. If a given item of justification depends on another belief for its justification, one can also reasonably ask for this latter justification to be provided, and so forth. This appears to lead to an infinite regress, with each belief justified by some further belief. The apparent impossibility of completing an infinite chain of reasoning is thought by some to support skepticism. The skeptic will argue that since no one can complete such a chain, ultimately no beliefs are justified and, therefore, no one knows anything. However, many epistemologists studying justification have attempted to argue for various types of chains of reasoning that can escape the regress problem.

Some philosophers, notably Peter Klein in his "Human Knowledge and the Infinite Regress of Reasons", have argued that it's not impossible for an infinite justificatory series to exist. This position is known as "infinitism". Infinitists typically take the infinite series to be merely potential, in the sense that an individual may have indefinitely many reasons available to him, without having consciously thought through all of these reasons. The individual need only have the ability to bring forth the relevant reasons when the need arises. This position is motivated in part by the desire to avoid what is seen as the arbitrariness and/or circularity of its chief competitors, foundationalism and coherentism.

Foundationalists respond to the regress problem by claiming that some beliefs that support other beliefs do not themselves require justification by other beliefs. Sometimes, these beliefs, labeled "foundational", are characterized as beliefs that one is directly aware of the truth of, or as beliefs that are self-justifying, or as beliefs that are infallible. According to one particularly permissive form of foundationalism, a belief may count as foundational, in the sense that it may be presumed true until defeating evidence appears, as long as the belief seems to its believer to be true.Template:Fact Others have argued that a belief is justified if it is based on perception or certain a priori considerations.

The chief criticism of foundationalism is that it allegedly leads to the arbitrary or unjustified acceptance of certain beliefs.Template:Fact

Another response to the regress problem is coherentism, which is the rejection of the assumption that the regress proceeds according to a pattern of linear justification. The original coherentist model for chains of reasoning was circular.Template:Fact This model was broadly repudiated, for obvious reasons.Template:Fact Most coherentists now hold that an individual belief is not justified circularly, but by the way it fits together (coheres) with the rest of the belief system of which it is a part.Template:Fact This theory has the advantage of avoiding the infinite regress without claiming special, possibly arbitrary status for some particular class of beliefs. Yet, since a system can be coherent while also being wrong, coherentists face the difficulty in ensuring that the whole system corresponds to reality.

There is also a position known as "foundherentism". Susan Haack is the philosopher who conceived it, and it is meant to be a unification of foundationalism and coherentism. One component of this theory is what is called the "analogy of the crossword puzzle". Whereas, say, infinists regard the regress of reasons as "shaped" like a single line, Susan Haack has argued that it is more like a crossword puzzle, with multiple lines mutually supporting each other.Template:Fact

Experience and aprioricity[]

For centuries, a distinction has been made between two kinds of knowledge—a posteriori and a priori.

  • A posteriori knowledge is knowledge the attainment of which, if possible, involves reference to experience (here, "experience" usually means conscious states such as sensory or introspective awareness). A posteriori knowledge is also called "empirical".
  • A priori knowledge is knowledge that is supposed to be gained independently of experience (see Rationalism, below, for further clarification).

This distinction has been disputed by various philosophers. Additionally, it is often related to that made between analysis and synthesis.

Analytic/synthetic distinction[]

Some propositions are such that we appear to be justified in believing them just so far as we understand their meaning. For example, consider, "My father's brother is my uncle." We seem to be justified in believing it to be true by virtue of our knowledge of what its terms mean. Philosophers call such propositions "analytic". Synthetic propositions, on the other hand, have distinct subjects and predicates. An example of a synthetic proposition would be, "My father's brother has black hair."

Although the American philosopher W. V. O. Quine, in his "Two Dogmas of Empiricism", famously challenged it, leading to its being taken to be less obviously real than it once seemed, it is still widely believed that there is a distinction between analysis and synthesis.Template:Fact

Specific theories of knowledge acquisition[]


In philosophy generally, empiricism is a theory of knowledge emphasizing the role of experience. Certain forms treat all knowledge as empirical,Template:Fact while some regard disciplines such as mathematics and logic as exceptions.Template:Fact



Rationalists believe that knowledge is primarily (at least in some areas) acquired by a priori processes or is innate—e.g., in the form of concepts not derived from experience. The relevant theoretical processes often go by the name "intuition".Template:Fact The relevant theoretical concepts may purportedly be part of the structure of the human mind (as in Kant's theory of transcendental idealism), or they may be said to exist independently of the mind (as in Plato's theory of Forms).

The extent to which aprioricity is emphasized over experience as a means to acquire knowledge varies from rationalist to rationalist. Some hold that knowledge of any kind can only be gained a priori,Template:Fact while others claim that some knowledge can also be gained a posteriori.Template:Fact As such, the borderline between rationalist epistemologies and others can be vague.


Constructivism is a view in philosophy according to which all knowledge is "constructed" inasmuch as it is contingent on convention, human perception, and social experience.Template:Fact It originated in sociology under the term "social constructionism" and has been given the name "constructivism" when referring to philosophical epistemology, though "constructionism" and "constructivism" are often used interchangeably.Template:Fact

What do people know?[]

The last question that will be dealt with is the question of what people know. At the heart of this area of study is skepticism, with many approaches involved trying to disprove some particular form of it.

General skepticism[]


Responses to general skepticism[]


Contextualism in epistemology is the claim that knowledge varies with the context in which it is attributed. More precisely, contextualism is the claim that, in a sentence of the form, "S knows that P," the relation between S and P depends on the context of discussion. According to the contextualist, the term "knows" is context-sensitive in a way similar to words such as "poor", "tall", and "flat". (Opposed to this contextualism are several forms of what is called "invariantism", the theory that the meaning of the term "knowledge", and hence the proposition expressed by the sentence, "S knows that P," does not vary from context to context.) The motivation behind contextualism is the idea that, in the context of discussion with an extreme skeptic about knowledge, there is a very high standard for the accurate ascription of knowledge, while in ordinary usage, there is a lower standard. Hence, contextualists attempt to evade skeptical conclusions by maintaining that skeptical arguments against knowledge are not relevant to our ordinary usages of the term.


For most of philosophical history, "knowledge" was taken to mean belief that was true and justified to an absolute certainty.Template:Fact Early in the 20th Century, however, the notion that belief had to be justified as such to count as knowledge lost favour. Fallibilism is the view that knowing something does not entail certainty regarding it. As a response to skepticism...


Specific forms of skepticism and responses to them[]

Skepticism about the external world[]


Skepticism about ethics[]


Skepticism about religious claims[]



References and further reading[]

  • Annis, David. 1978. "A Contextualist Theory of Epistemic Justification", in American Philosophical Quarterly, 15: 213-219.
  • Boufoy-Bastick, Z. 2005. "Introducing 'Applicable Knowledge' as a Challenge to the Attainment of Absolute Knowledge", Sophia Journal of Philosophy, 8: 39-51. Online PDF.
  • Bovens, Luc & Hartmann, Stephan. 20003. Bayesian Epistemology. Oxford: Oxford University Press.
  • Butchvarov, Panayot. 1970. The Concept of Knowledge. Evanston, Northwestern University Press.
  • Cohen, Stewart. 1998. "Contextualist Solutions to Epistemological Problems: Scepticism, Gettier, and the Lottery." Australasian Journal of Philosophy, 76: 289-306.
  • Cohen Stewart. 1999. "Contextualism, Skepticism, and Reasons", in Tomberlin 1999.
  • DeRose, Keith. 1992. "Contextualism and Knowledge Attributions", Philosophy and Phenomenological Research, 15: 213-19.
  • DeRose, Keith. 1999. "Contextualism: An Explanation and Defense", in Greco and Sosa 1999.
  • Feldman, Richard. 1999. "Contextualism and Skepticism", in Tomberlin 1999, pp. 91-114.
  • Gettier, Edmund. 1963. "Is Justified True Belief Knowledge?", Analysis, Vol. 23, pp. 121-23. Online text.
  • Greco, J. & Sosa, E. 1999. Blackwell Guide to Epistemology, Blackwell Publishing.
  • Hawthorne, John. 2005. "The Case for Closure", Contemporary Debates in Epistemology, Peter Sosa and Matthias Steup (ed.): 26-43.
  • Hendricks, Vincent F. 2006. Mainstream and Formal Epistemology, New York: Cambridge University Press.
  • Keeton, Morris T. 1962. "Empiricism", in Dictionary of Philosophy, Dagobert D. Runes (ed.), Littlefield, Adams, and Company, Totowa, NJ, pp. 89–90.
  • Kirkham, Richard. 1984. "Does the Gettier Problem Rest on a Mistake?" Mind, 93.
  • Klein, Peter. 1981. Certainty: a Refutation of Scepticism, Minneapolis, MN: University of Minnesota Press.
  • Kyburg, H.E. 1961. Probability and the Logic of Rational Belief, Middletown, CT: Wesleyan University Press.
  • Lewis, David. ?. "Elusive Knowledge." Australian Journal of Philosophy, 74, 549-67.
  • Rand, Ayn. 1979. Introduction to Objectivist Epistemology, New York: Meridian. Online text.
  • Russell, Bertrand. 1912. The Problems of Philosophy, New York: Oxford University Press. Online text.
  • Schiffer, Stephen. 1996. "Contextualist Solutions to Scepticism", Proceedings of the Aristotelian Society, 96:317-33.
  • Steup, Matthias. 2005. "Knowledge and Scepticism", Contemporary Debates in Epistemology, Peter Sosa and Matthias Steup (eds.): 1-13.
  • Wittgenstein, Ludwig. 1922. Tractatus-Logico Philosophicus, C.K. Ogden (trns.), Dover. Online text.

External links and references[]

Stanford Encyclopedia of Philosophy articles:

Other links:

See also[]

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