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What Is Epistemology?

A Brief Introduction to the Topic

Keith DeRose,
Yale University
Dept. of Philosophy

I suppose many are in the position of knowing that epistemology is a branch of philosophy, but not knowing anything beyond that. (Well, not knowing anything further about what epistemology is — let’s not get into general skepticism just yet!)  The standard very short answer to our title question is that epistemology is the theory of knowledge.  In fact, so far as I can tell, “epistemology” and “theory of knowledge” are used interchangeably in, for instance, college course catalogues.  Epistemology, then, is the branch of philosophy that deals with questions concerning the nature, scope, and sources of knowledge.  In what follows, I’ll briefly describe a few of the issues epistemologists deal with.  That should give you a bit better idea of what epistemology is, and, for those considering taking an epistemology class, what to expect from such a class.  For those interested in further reading, there are links at the bottom of this page to articles that are introductory in nature (mostly from the Stanford Encyclopedia of Philosophy, a great on-line resource) on particular topics in epistemology.


1. Under what Conditions Does One Know?: The Analysis of Knowledge.

Since epistemology is the theory of knowledge, a central question of the area is: Under what conditions does a subject know something to be the case?  Most general epistemology classes (as opposed to specialized advanced courses that zero in on a particular epistemological topic) spend at least some time on this question, and many begin with it.
A very important paper on this topic — perhaps the most commonly assigned paper in epistemology classes — is Edmund Gettier’s short classic, “Is Justified True Belief Knowledge?” (Analysis 23 (1963): 121-123 [in the journal Analysis, volume 23, published in the year 1963, on pages 121-123]), available on-line here.  Gettier’s target is an initially tempting account of knowledge: the “JTB” account, as it’s often called, which analyzes knowledge as justified true belief.  According to such an account, a subject S knows that P if and only if (Gettier uses the common philosophical abbreviation of IFF for “if and only if”):
1. P is true,
2. S believes that P, and
3. S is justified in believing that P.
According to this account, then, you know that it’s raining outside, for example, if and only if it is true that it’s raining outside, and you believe that it’s raining outside, and you are justified in so believing.  To refute such accounts, Gettier advanced two examples, each of which involve (or at least intuitively seem to involve) instances of justified true belief that nonetheless fail to be instances of knowledge.
One could try to maintain the JTB account in the face of Gettier’s cases either by arguing (against appearances) that the the true beliefs in question in these examples are not really justified, or by maintaining (again against initial appearances) that the subjects in the examples really do know the propositions in question.  But most epistemologists have accepted that Gettier’s cases are genuine counter-examples to the JTB theory — they are genuine examples of situations in which the questions “Does S know that P?” and “Does S have a justified true belief that P?” get different answers, and thus refute the JTB account of knowledge.
Gettier’s paper spawned an explosion of philosophical literature aimed at producing an acceptable account of knowledge, either by modifying the JTB account by adding further conditions to it, or by replacing the third, justification, condition with one or more other conditions.  Many new accounts were proposed, only to be subjected to new counter-examples — examples which refute the account in question either by showing how a subject can know something despite failing to meet the conditions the account proposes, or by showing how a subject can fail to know something even though she does meet the conditions proposed.  Often, still more sophisticated accounts were proposed to handle the new examples, only to crash on the rocks of still more sophisticated counter-examples.  (For discussion of many examples of the analyses in question, and of some of the troubles they run into, see Robert Shope’s book, The Analysis of Knowledge (Princeton University Press, 1983).)  Many epistemologists grew tired of the game, and despaired of coming up with an account of knowledge that could survive this process.  A widely discussed topic has been whether and how the methodology of testing philosophical accounts against examples (a methodology that is practiced in many areas of philosophy besides epistemology) can be profitably pursued, and the “post-Gettier” literature on the analysis of knowledge has been used as exhibit A of this methodology in action.
[For more introductory material on this topic, see Matthias Steup’s Stanford Encyclopedia of Philosophy article, “The Analysis of Knowledge”.]

2. Justification and Other Epistemic Concepts.

As the above discussion shows, one issue that arises in discussions of whether and when subjects know something is whether and when they are justified in believing things, and the justification of beliefs is a standard topic in epistemology.  Epistemology also concerns itself with other, closely related concepts.  Some examples: When is a subject rational in believing something?  When are you certain of something?  When do you know for certain that something is the case?  When is something doubtful, for a subject, or not?  When is something possible (in an epistemic sense of “possible”) — under what conditions is a belief possibly false from its subject’s point of view?  When is a belief adequately supported by one’s evidence?  (And what constitutes our evidence for our beliefs, and when does a belief need to be supported by evidence in order to be rational?)  All of these are epistemological topics in their own right, of interest beyond what contribution an understanding of these concepts might make in a successful account of knowledge.

3. What Do We Know?: Skepticism.

As one would expect, another central question in the theory of knowledge is: What do we know?  What is the scope or extent of our knowledge?  This question, of course, is closely related to the question, addressed above in section 1, of what it takes to know something.
Pessimistic accounts of the scope of our knowledge have it that we know less than we think we know; radically pessimistic accounts have it that we know very little, or perhaps even nothing!  Though radical, such skeptical accounts of the scope of our knowledge have been the center of much philosophical attention, both historically and in recent epistemological work.  Usually, skepticism is something philosophers attack and try to overcome; occasionally, it is defended.  The attention paid here is in part due to the presence of powerful skeptical arguments that threaten to show that skeptical assessments of the scope of our knowledge are actually correct.  A central epistemological obsession has been showing what is wrong with these skeptical arguments — or, occasionally, arguing that there’s nothing wrong with them.
A skeptical thesis is typically a claim that the beliefs in a certain range lack a certain status. In addition, then, to varying in their scope — which specifies the range of beliefs being targeted — skeptical theses, and the arguments used to establish them, also differ in their force — which specifies precisely what lack the skeptic alleges befalls the targeted beliefs. Skepticism, then, isn’t limited to pessimistic accounts of the extent of our knowledge; they can be views on which any of the designations discussed above in section 2 surprisingly fail to apply to a wide range of our beliefs.  Theories according to which surprisingly few, or perhaps none, of our beliefs are justified, or rational, or adequately supported by our evidence, or known with complete certainty, etc., are also examples of skepticism.
[For more introductory material on skepticism, including a description of some common skeptical arguments, and many of the most influential types of response to skeptical problems, see my “Responding to Skepticism,” available on-line here.]

4. Internalism and Externalism.

As we’ve already noted, epistemologists are interested in the matters of when (under what conditions) beliefs are justified and when subjects know what they believe.  There is an important division between two main types of accounts of these matters — that between internalism and externalism.  According to the epistemic internalist, these matters depend primarily on factors internal to the believer’s point of view and/or factors to which the believer has special access. Most internalists accept that the external matter of whether a belief is true is relevant to the issue of whether it constitutes knowledge, so on the issue of knowledge, internalism is usually the position that only or primarily internal factors are relevant to whether true beliefs constitute knowledge. The epistemic externalist, on the other hand, claims that issues of knowledge and/or justification depend exclusively or primarily on such factors as how the belief was caused or how reliable is the faculty or mechanism by which the subject came to hold the belief — matters which are not in the requisite way “internal” to the subject’s point of view, as can be seen by the fact that you can imagine two subjects whose mental lives are identical with respect to how things seem to them from their own point of view, but whose beliefs diverge with respect to the matters in question. The internalist about justification will have to hold that the beliefs of such subjects have the same justificatory status (they’re either both justified or both unjustified, and to the same degree), and the internalist about knowledge will have to hold that, so long as the beliefs of such “twins” are true in both cases, they can’t diverge on the matter of whether they constitute knowledge.

So, consider an “internal twin” of me.  This twin’s life was identical to mine up to midnight last night.  At that time, our life histories drastically diverge, but not in any way causes a difference in what our experiences seem like from the inside: Our “internal” lives are still identical.  At midnight, super-advanced aliens snatched my twin’s brain from his body, placed it in a (human)-brain-sustaining vat, and hooked it up to a super-advanced computer, that, taking into account the output of the brain that is my twin, gives it appropriate sensory input.  Meanwhile, we may suppose, I remain a normally embodied human, with no aliens anywhere around me.  The aliens who snatched my twin’s brain from his body are so advanced that they were able to do so in such a way that did not impact at all on his experience.  Now it is morning, and I have a conversation with my wife.  My twin is having identical experiences, and so thinks he is having a conversation with his wife, but in fact he is not.  (Hiswife is in fact now, unbeknownst to him, in shock and mourning over the discovery of his de-brained, dead body.)  The internalist about justification will hold that my belief that I am having a conversation with my wife has the same justificatory status as does my twin’s analogous belief: either we are both justified in our belief or both unjustified, and to the same degree.  For what it’s worth, the internalist has always seemed to me to be right about this: It seems to me that such twins can’t differ from one another on the justificatory status of their beliefs: If my belief is justified, so is my twin’s; if his is unjustified, so is mine.  In the case under discussion, I think both me and my twin are justified in holding the belief in question — even though my twin’s belief is false.

What about knowledge?  Since my belief (that I’m having a conversation with my wife) is true, while my twin’s belief is false, even internalists, at least as I construe them, can hold that one of us (presumably, me) knows the item in question, while the other (presumably, my twin) doesn’t.  For a good test case, we need an example where the beliefs in question are both true.  So: I am holding a cup of coffee.  My twin also believes he is holding a cup of coffee, but in fact he isn’t.  Because I (correctly) believe I am holding a cup of coffee, I believe that there is a cup of coffee within 10 feet of my brain.  (If you are not a fan of “implicit” beliefs, you may suppose that I have just been asked whether there is a cup of coffee within 10 feet of my brain, and so have considered the matter and have come to a positive conclusion, and, of course, then, that my twin has had experiences that make him think that he has just been asked whether there is a cup of coffee within 10 feet of his brain, and has come to a positive conclusion.)  So my twin also believes there is a cup of coffee within 10 feet of his brain.  He believes this because he (incorrectly) believes that he is holding a cup of coffee.  But while he is wrong about the matter of what he is holding, let us suppose that he turns out to be right about the fact that there is a cup of coffee within 10 feet of his brain: The aliens who have snatched his brain have taken up the human practice of drinking cups of coffee, and one of the aliens has carelessly left a cup of coffee resting right next to the vat that holds the brain of my internal twin.  So, as it happens, my twin’s belief that there is a cup of coffee within 10 feet of his brain is true.  So here we have a pair of “twins” who share a certain belief that is true in both of their cases.  The internalist will say that either both me and my twin know that there is a cup of coffee within 10 feet of his brain, or that neither of us knows that.  Since it seems to me that I do know know that there is a cup of coffee within 10 feet of my brain, but that my twin doesn’t know that of himself, the externalist seems to me to be right about knowledge.  Knowledge seems to me to crucially involve matters that go beyond true belief plus purely “internal” issues: there are “external” matters beyond the truth of the belief in question that matter to whether a belief is a piece of knowledge.  (Since I think my twin is, like me, justified in believing there is a cup of coffee within 10 feet of his brain, but does not know that this is true, even though it in fact is true, I think the case of my twin’s belief that there is a cup of coffee within 10 feet of his brain is a “Gettier case,” in one common use of that term: It is a case of a justified, true belief that is nevertheless not a piece of knowledge.)

5. The Structure of Knowledge: Foundationalism and Coherentism.

An important issue for epistemologists is over the structure of knowledge (or of justification).  The main positions on this issue, foundationalism and coherentism, are perhaps best introduced as reactions to the problem of the regress of reasons.  At least sometimes, a belief, A, constitutes a piece of knowledge or is justified because it is based on another belief, B, that one holds and that constitutes evidence for A.  But it seems this can only work if belief B is itself a piece of knowledge or is a justified belief.  But how did B get to be justified?  Perhaps it was based on still another of one’s beliefs, C.  But, again, it seems this can only work if C is already justified or known.  Where and how can the process of basing beliefs on other beliefs come to an end?  If we demand of all of our beliefs that they be properly based on evidence in the form of other beliefs we hold in order to be justified, and if we demand that the lines of evidence contain no “circles” of justification (that it can never happen that A is justified because it is based on B, which is justified because it is based on C, and so on, until we reach a belief that is justified because it is based on A), and if we admit that these lines of evidence cannot be infinitely long, we will be led to the skeptical conclusion that none of our beliefs are justified (or are knowledge, if we run this problem on knowledge rather than justification).
Foundationalists avoid this skepticism by denying that all of our beliefs need to be based on other of our beliefs in order to be justified.  According to the foundationalist, some of our beliefs are properly basic (to use a term that, as far as I know, originated with Alvin Plantinga): they are justified (or are knowledge) independent of their being based on any other beliefs.  These properly basic beliefs then serve as the “foundation” upon which all of the rest of our justified beliefs are “built”: All of our justified beliefs that are not properly basic are based, directly or indirectly, upon this foundation of properly basic beliefs.  Foundationalism itself is just a commitment to this basic structural picture.  Versions of foundationalism will differ with one another over the matter of which of our beliefs can be properly basic (can be justified without being based on other of our beliefs), and over what constitutes a successful basing of one belief upon another.
Coherentists hold that only evidence-like relations among one’s beliefs can render any of our beliefs justified, and they thus reject the foundationalist’s properly basic beliefs.  The coherentist instead avoids the regress argument by accepting that there can be “circles” of justification: sometimes A can be justified by being based on B, which is (perhaps indirectly, through a long series of basings) based on A.  What renders our beliefs justified on the coherentist picture is how well our beliefs cohere with one another, rather than on how well they are based on some foundation of “properly basic” beliefs.  Again, coherentism itself is just a commitment to this basic picture of the structure of our justified beliefs, and this basic picture gets worked out in a myriad of significantly different ways.
I should stress that although it’s handy to introduce these basic structural options as responses to the regress argument, advocates of these positions don’t necessarily come to these positions just in order to avoid the regress argument.
While, as I have stressed above, there are many significantly different versions of both foundationalism and coherentism, there are also views that fall into the gap between these two camps, and represent something of a compromise between them.  (On this, you can see my paper, “Direct Warrant Realism” [pdf, word], where, in sections 2-4, I defend the such a structural compromise position, and, in section 1, I explain, and in sections 5-7 I defend a particular account of the justification of perceptual beliefs — “Direct Warrant Realism” — that exemplifies this compromise structure.)

Other Topics

The above is just a sample of the kinds of topics treated by epistemologists.  Other epistemologists no doubt would have chosen different sets of topics to explain.  Still, the above quick discussion should serve to give you some idea of the type of issues treated in epistemology — and there are some links to some encyclopedia articles on various other topics below.  If you want to dig more deeply, one good place to go next is one of the anthologies listed toward the bottom of section 2 of The Epistemology Page.  See the different topics into which essays are organized, in, for instance, the Sosa & Kim, ed. anthology, Epistemology, and then you will also have at hand some of the more important essays on the topics that interest you.

If others inform me of good brief introductory explanations of important topics in epistemology that are available on-line, I will post links to them here.

See Also These Introductory On-Line Articles:

On Epistemology in general:
Joseph Cruz’s Nature Encyclopedia of Cognitive Science article, “Epistemology” (pdf document)
Peter Klein’s Routledge Encyclopedia of Philosophy article, “Epistemology”.

On Particular topics in epistemology:
Elizabeth Anderson’s Stanford Encyclopedia of Philosophy article, “Feminist Epistemology and Philosophy of Science”.
Tim Black’s Internet Encyclopedia of Philosophy article, “Contextualism in Epistemology”.
Michael Brady and William Harms’s Stanford Encyclopedia of Philosophy article, “Evolutionary Epistemology”.
Keith DeRose’s editor’s introduction to Skepticism: A Contemporary Reader, “Responding to Skepticism”.
Richard Feldman’s Stanford Encyclopedia of Philosophy article, “Naturalized Epistemology”.
Peter Forrest’s Stanford Encyclopedia of Philosophy article, “The Epistemology of Religion”.
Richard Fumerton’s Stanford Encyclopedia of Philosophy article, “Foundationalist Theories of Epistemic Justification”.
Alvin Goldman’s Stanford Encyclopedia of Philosophy article, “Social Epistemology”.
John Greco’s Stanford Encyclopedia of Philosophy article, “Virtue Epistemology”.
Jonathan Kvanvig’s Stanford Encyclopedia of Philosophy article, “Coherentist Theories of Justification”.
George Pappas’s Stanford Encyclopedia of Philosophy article, “Internalist vs. Externalist Conceptions of Epistemic Justification”.
Matthias Steup’s Stanford Encyclopedia of Philosophy article, “The Analysis of Knowledge”.

For a defense of what he calls “veritistic epistemology” [“Veristic epistemology (whether individual or social) is concerned with the production of knowledge, where knowledge is here understood in the ‘weak’ sense of true belief.  More precisely, it is concerned with both knowledge and its contraries: error (false belief) and ignorance (the absence of true belief).  The main question for veritistic epistemology is: Which practices have a comparatively favorable impact on knowledge as contrasted with error and ignorance?” (p. 5)] against “such views as social constructivism, postmodernism, pragmatism, cultural studies, and critical legal studies” (p. 7), see:
-Alvin Goldman’s “Epistemology and Postmodern Resistance” (pdf document; note that there are a couple of blank pages at the beginning of the document), which is the first chapter of Goldman’s Knowledge in a Social World (Oxford University Press, 1999).

For my best attempt to say what postmodernism is, and why I tend not to like it, with lots of links to material I’ve found helpful, see my blog post, “Characterizing a FogbankWhat Is Postmodernism and Why Do I Take Such a Dim View of It?”.


Keith DeRose
Last modified 23 November 2005


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