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Definition: epistemology from Philip's Encyclopedia

Branch of philosophy that critically examines the nature, limits and validity of knowledge, and the difference between knowledge and belief. Descartes showed that many previously 'philosophical' questions would be better studied scientifically, and that what remained of metaphysics should be absorbed into epistemology.

Summary Article: Epistemology from Encyclopedia of Philosophy & the Social Sciences

Epistemology is the philosophical subdiscipline that studies the evaluative dimensions of cognition, their metaphysical bases, and, increasingly nowadays, the language we use to ascribe cognitive achievements. The nature and scope of knowledge is the central focus of epistemology.

Knowledge and Assertion

Assertion is a speech act whereby we communicate to our audience that a certain proposition is true, and it is the main way we communicate information to one another. Given that we rely so pervasively on assertions, it is natural to wonder what the standards ought to be for our assertions and whether we as assertors live up to them? Research into the epistemic norms of assertion is one of the most exciting and rapidly growing fields within philosophy. Within this field, the leading proposal is that knowledge is the norm of assertion, a view known as the knowledge account of assertion.

The knowledge account of assertion says that knowledge sets the standard for permissible assertion: You may assert P only if you know that P is true. The primary evidence for the knowledge account is an explanatory inference from linguistic data, in particular conversational patterns surrounding the give-and-take of assertion. For example, typically, when you make an assertion, even when the content of your assertion has nothing to do with you or what you know, it is appropriate to ask you “How do you know that?” The knowledge account explains the appropriateness of the question as follows: In making the assertion, you represent yourself as having the authority to do so, and knowledge is what gives you the authority, rendering it sensible to ask how you know that. Similarly, if someone makes an assertion, the response “You don't know that” is taken as an outright rejection of his or her authority to make the assertion, which the knowledge account easily explains. Also, when someone asks you a question, even when the question has nothing to do with you or what you know, it is typically appropriate for you to respond, “I don't know.” The knowledge account explains why it is appropriate: By saying “I don't know,” you inform the questioner that you lack the authority to answer the question.

Those attracted to the knowledge account of assertion are often attracted to related views about practical reasoning, action, and belief, namely, that knowledge is the norm of these too. These other three accounts are also supported by linguistic data and patterns of appraisal, though the overall case for them is generally regarded as weaker than the case for the knowledge account of assertion.

Furthermore, investigation into the epistemic norms of assertion, reasoning, action, and belief presents opportunities for collaboration among epistemologists and social and cognitive scientists.


Skepticism perennially fascinates philosophers. It is almost unanimously accepted that skepticism is false, so one main question is “Why do skeptical challenges nevertheless seem so formidable?” For example, it usually seems obvious that when you say, for instance, “I know that I have hands,” you speak truthfully. But do you know that you are not a handless brain in a vat (BIV) being perfectly deceived into thinking that you have hands? Most people hesitate at this question, and many go so far as to say, “No, I don't know that I'm not a handless BIV.” Yet if you know that you have hands, then you seem to be in an ideal position to simply deduce, and thereby know, that you are not a handless BIV. So why are we tempted to say “I don't know” in such a situation?

Setting aside extravagant skeptical scenarios featuring BIVs, we see a similar effect when speakers move from an ordinary context to a high-stakes context. If a fellow traveler in an airport looks up from his magazine and nonchalantly asks, “I'm bored. Do you know whether this flight we're about to board goes directly to Chicago?” You might check the board, see that it says “Direct flight to Chicago” and respond, “Yes, I happen to know that it does.” But suppose that instead of being asked by a nonchalant fellow traveler, you are asked the same question by an organ courier transporting an organ to a patient in Chicago, which will spoil unless she takes a direct flight to Chicago. Now, even if the board says “Direct flight to Chicago,” it would be natural for you to respond by saying, “No, sorry, I don't know. Maybe you should go ask the captain.” Again, why are we tempted to say “I don't know” in such a situation?

In recent years, some epistemologists have proposed a semantic solution to the apparent conflict in what we are willing to say about knowledge in ordinary contexts versus what we say when confronted with skeptical hypotheses or high-stakes decisions. Epistemic contextualism is the view that the cognitive verb knows, as it features in propositional knowledge ascriptions such as “I know that P” and “You don't know that P,” is a context-sensitive term. The truth conditions of “I know that this is a direct flight” are different in an ordinary context from those in a high-stakes context; in an ordinary context, less evidence is required for you to truly say “I know that this is a direct flight” or “I have hands” than is required in a context where the stakes are high or where serious skeptical hypotheses have been raised. Thus, the contextualist can maintain both that we typically speak truthfully when we say “I know this” or “I know that” and that the skeptic speaks truthfully when he says “You don't know this” or “You don't know that.” Despite appearances, what the skeptic says does not contradict what we ordinarily say, just as I do not contradict you when I say (in Vancouver) “It's raining here” and you say (in Paris) “It's not raining here.”

Contextualists disagree over the correct semantic model for “knows.” Some contextualists say that “knows” is an indexical expression, similar to the pronoun I or the adverb yesterday. Others liken it to gradable adjectives, such as tall and flat. But both of those semantic models have been severely criticized. A more recent suggestion is that knowledge ascriptions are context-sensitive not because “knows” is context-sensitive but because in general the propositional content of speech acts is context-sensitive and knowledge ascriptions are no exception. The semantics of “knows” and knowledge ascriptions is ripe for interdisciplinary collaboration between epistemologists and linguists. Research into the psychology of judgments made in high-stakes contexts or in the context of skeptical challenges could also be highly relevant to sorting out the linguistic data. And anthropological data on the linguistic behavior of humans in other cultures could highlight further important data and theoretical possibilities.

The Value of Knowledge

It is a virtual platitude that knowledge is intellectually better than mere true belief. Going all the way back to Plato's dialogue Meno, philosophers have asked why this is so. One deceptively simple answer is that knowledge is better because it has greater practical value than true belief. But Plato ruled this out when he first raised the question, noting, for example, that merely truly believing this is the road to Larissa will get you to Larissa just as well as knowing that this is the road to Larissa will. So not only does it seem correct that knowledge is better than mere true belief, it also seems that knowledge's added value is not merely practical. Some epistemologists contend furthermore that knowledge is better than mere true belief not only in degree but also in kind: Knowledge has a kind of intellectual value that mere true belief lacks.

It is widely accepted that an adequate theory of knowledge must explain knowledge's special value, though this is not entirely uncontroversial. There is a consensus, however, that it is at least a good thing for a theory to explain knowledge's value.

Several theories have been proposed to explain knowledge's value. On one view, knowledge is valuable because it is the most general factive propositional attitude. Factive propositional attitudes are attitudes that you can have only toward a true proposition; this class of attitudes includes remembering that P, perceiving that P, and being aware that P. To say that knowledge is the most general factive propositional attitude is to say that the following is a necessarily true generalization: If you bear any factive propositional attitude toward the proposition P, then you know that P. We value a match between mind and world, and knowing is the most general attitude in which the mind must match the world, which according to this view explains why knowledge is specially valuable.

A different proposal begins by pointing out that while it is, of course, good to have good things, it is even better to merit or earn the good things you have. For example, other things being equal, it is better to earn your fortune than to win it through the lottery. Put otherwise, it is better to succeed through skill and effort than through luck. So if knowledge were true belief for which you earn credit or if knowledge were true belief manifesting intellectual skill, then that would explain why knowledge is better than mere true belief. For then the superiority of knowledge would just be a special case of the superiority of earning something good or achieving it through skill, as opposed to just getting lucky. This explanation of knowledge's value is distinctive of an increasingly popular approach in epistemology called virtue epistemology.

The Gettier Problem

Perhaps the most important development in epistemology over the past 50 years was the research program ignited by Edmund Gettier's three-page article published in 1963, “Is Justified True Belief Knowledge?” Many philosophers at the time thought that knowledge could be defined as justified true belief (JTB for short). Gettier presented what most philosophers took to be decisive counterexamples to the JTB account of knowledge. These examples were taken to show that JTB is not sufficient for knowledge—that something more than JTB is required.

Gettier cases follow a recipe. Start with a belief sufficiently justified to meet the justification requirement on knowledge. Then, add an element of bad luck that would normally prevent the justified belief from being true. Last, add a dose of good luck that counteracts the bad luck, so that the belief ends up true anyhow. It has proven difficult to explain why this “double-luck” structure prevents knowledge.

Philosophers have proposed dozens of hypotheses to handle these “Gettier cases,” as they came to be called. It is widely assumed that an acceptable theory of knowledge must explain what goes wrong in Gettier cases. No-false-basis theorists argued that knowledge is JTB, which is not essentially based on a falsehood, but Gettier cases all involve beliefs essentially based on a falsehood. Defeasibility theorists argued that knowledge is JTB, for which there is no further fact such that it would defeat the subject's justification if she learned of it, but Gettier cases all involve facts that defeat justification. Reliabilists argued that knowledge is reliably produced true belief, but Gettier cases are examples of unreliably produced belief. Causal theorists argued that knowledge is true belief nondeviantly caused by the fact believed to be true, but the right kind of causal link is missing in Gettier cases. Counterfactual theorists argued that knowledge is true belief that has the right counterfactual relationship to the truth believed (the believer would get it right across a relevant class of counterfactual scenarios), but in Gettier cases, the relevant counterfactual relation is missing. Virtue epistemologists argue that knowledge is true belief manifesting intellectual virtue, but in Gettier cases, the subject's true belief fails to manifest her virtue.

None of these solutions has been widely accepted. At least a few epistemologists claim that the entire literature on the Gettier problem is mistaken because it falsely presupposes that the subject in a Gettier case lacks knowledge. On one such view, knowledge is merely true belief, though this view is almost universally rejected.

Epistemology and Experimental Philosophy

Experimental philosophers have made a very interesting and potentially significant sociological observation: People from East Asian cultures have a greater tendency than people from Western cultures to judge that the subject in a Gettier case has knowledge. More generally, results from experimental philosophy demonstrate that differences in gender, age, socioeconomic status, and culture are often associated with statistically significant differences in intuitive judgments about thought experiments of the sort Gettier used and that philosophers routinely rely on in the course of debate and inquiry. Uncovering these often very surprising differences and understanding their significance is an area of extremely fruitful and rapidly increasing collaboration among philosophers and psychologists.

See also

Common Knowledge

Epistemology of Mass Collaboration


Experimental Philosophy

Feminist Epistemology


Social Epistemology

Speech Acts

Virtue Epistemology

Further Readings
  • Dancy, J.; Sosa, E.; Steup, M. (Eds.). (2011). A companion to epistemology. Wiley-Blackwell Malden, MA.
  • DeRose, K. (2009). The case for contextualism. Oxford University Press Oxford, England. doi:10.1093/acprof:oso/9780199564460.001.0001.
  • Gettier, E. (1963). Is justified true belief knowledge? Analysis, 23, 121-123. doi:10.1093/analys/23.6.121.
  • Haddock, A.; Millar, A.; Pritchard, D. (Eds.). (2009). Epistemic value. Oxford University Press Oxford, England. doi:10.1093/acprof:oso/9780199231188.001.0001.
  • Hawthorne, J.; Stanley, J. (2008). Knowledge and action. Journal of Philosophy, 105, 571-590.
  • Knobe, J.; Nichols, S. (Eds.). (2008). Experimental philosophy. Oxford University Press Oxford, England.
  • Sosa, E. (2007-2009). Apt belief and reflective knowledge (Vols. 1-2). Oxford University Press Oxford, England.
  • Sosa, E.; Kim, J.; Fantl, J.; McGrath, M. (Eds.). (2008). Epistemology: An anthology. Blackwell Malden, MA.
  • Stainton, R. (2010). Contextualism in epistemology and the context-sensitivity of “knows.” In J. Campbell; M. O‘Rourke; H. Silverstein (Eds.), Knowledge and skepticism (pp. 137-163). MIT Press Cambridge.
  • Steup, M.; Turri, J.; Sosa, E. (2012). Contemporary debates in epistemology (2nd ed.). Wiley-Blackwell Malden, MA.
  • Turri, J. (2011). The express knowledge account of assertion. Australasian Journal of Philosophy, 89, 37-45. doi:10.1080/00048401003660333.
  • Williamson, T. (2000). Knowledge and its limits. Oxford University Press Oxford, England.
  • Zagzebski, L. (2009). On epistemology. Wadsworth Belmont, CA.
  • John Turri
    © 2013 SAGE Publications, Inc

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