In his remarkably short article, “Is Justified True Belief Knowledge?” (1963), Edmund Gettier succeeded in casting doubt on what had been one of the most widely accepted ideas in philosophy: that to know something is to have a belief that one can justify and which is true; a theory that goes at least as far back as Plato’s Theaetetus and which has been called the “Tripartite Theory of Knowledge” (TTK).
Gettier’s case against TTK is made via counterexamples. Gettier presents us with cases in which a person has a belief, P, which is true and for which he has justification, but which he nonetheless does not know. The cases are ingenious and rely on just two assumptions, both of which seem uncontroversial: (a) one can be justified in believing something that turns out to be false; (b) justification is transitive, such that if S is justified in believing P and Q follows logically from P, then S is justified in believing Q.
Gettier presents two cases that are needlessly complicated, so others have come up with “Gettier-style” cases that are simpler yet perform in precisely the same way as the originals. You can easily check out the original Gettier cases in the article, but here are two simpler cases that make the same point, which come from Jonathan Dancy’s Introduction to Contemporary Epistemology. (1985)
(I) Imagine that we are sitting together in a sports bar, watching the Wimbledon final between John McEnroe and Bjorn Borg, and suppose that we see John McEnroe win the match. As a result, we believe that John McEnroe has won Wimbledon and certainly are justified in that belief (if asked, we will say that we just watched him win on TV). Also imagine, however, that this year’s Wimbledon TV feed has gone down and that unbeknownst to us, we have been watching a rerun of last year’s much. Suppose also that John McEnroe won this year’s Wimbledon as well. Under such circumstances it would seem that even though we have a true, justified belief that John McEnroe has won Wimbledon, it would be very strange to describe us as knowing that McEnroe won.
(II) Imagine that we are driving through the countryside and observe a lone sheep on a distant hilltop, and as a result, we believe that there is a sheep there. But suppose that what we have seen is not a real sheep but rather a mock-up of a sheep. Suppose, in addition, that there is another sheep on the hill, behind it, that we cannot see. Once again, we have a belief that we are justified in holding and which is true, but it would be awfully odd to say that we know there is a sheep on the hilltop.
These cases – as well as Gettier’s originals – reflect two very common and well-understood facts about us and our “epistemic condition”: that we may stumble upon the truth entirely by accident or even by way of misleading information; and that what may seem, by every measure, to be the best reason in the world for believing something, may in fact turn out not to be a good reason at all.
There was an explosion of activity in the epistemological community after the publication of Gettier’s article. One prominent strategy was to add a defeasibility condition: S knows P, if S believes P, P is true, S is justified in believing P, and there are no defeating conditions (i.e. no statements that would overturn S’s justification). [1] This would render Gettier style cases harmless for TTK, for in each case, there is some statement that (had the person known it at the time) would have defeated the justification for the relevant belief. The trouble with this is that it’s not easy to define what counts as a defeating statement and furthermore, one can never be sure whether some further information might not come along that would defeat the defeater and render the original belief justified after all. [2] In taking into account such considerations, it becomes apparent that no belief could ever really be justified on this view, because no one could ever know whether there might be some potentially defeating statement of which one is not yet aware.
Another prominent strategy involves building a causal condition into our definition of knowledge, in the manner suggested by Alvin Goldman not long after Gettier’s paper was published. [3] For S to know P, his belief that P must – in some “appropriate” sense – be causally connected to P. (p. 369) This proposal avoids the Gettier counterexamples, because in each Gettier-style case, having the relevant true belief is lucky, rather than the result of being causally connected to the truth-maker. It’s not the sheep that makes me believe there is a sheep on the hill, but rather, a mock-up of a sheep. That there is an actual sheep is sheer luck. It’s not McEnroe’s win this year that makes me believe that he won Wimbledon, but rather, a rerun of last year’s match, which he also won.
The one downside – if it is a downside – to Goldman’s response is that it abandons a long and widely held view of justification: namely, that one’s justification for believing P ought to be some reason one has or reasoning one has engaged in. That is, justifications should consist of reasons held by the believer. This raises a much larger issue regarding the very nature of justification itself, one that has become a major topic of epistemological investigation in its own right under the name, “The Internalism/ Externalism” debate.
Notes:
[1] Keith Lehrer and Thomas Paxson, Jr., “Knowledge: Undefeated Justified True Belief,” The Journal of Philosophy, Vol. 66, No. 8 (Apr. 24, 1969), pp. 225-237.
[2] This is the idea behind the “Tom Grabit” case, in Lehrer and Paxson (1969).[3] Alvin I. Goldman, “A Causal Theory of Knowing,” The Journal of Philosophy, Vol. 64, No. 12 (Jun 22, 1967), pp. 357-372.
