<epistemology> a type of counterexample to the definition of knowledge as justified true belief. The first examples of the Gettier problem were published in 1963 by Edmund Gettier. In that paper, Gettier makes very clear that the tripartite definition concerns not knowledge per se, but a knowing subject's epistemic state:
S knows that p iff
1) p is true 2) S believes that p 3) S is justified in believing that pSceptical arguments usually accept (2) and (3) and try to show that, no matter how one reinforces these two conditions, (1) does not necessarily follow. Gettier-type counterexamples concern (3) and are not to be confused with sceptical arguments. They show that even if (1) and (2) are granted, one can always prove that S has merely guessed that p, since circumstances may be such that (3) only appears to apply, but actually does not, or is satisfied only in a sense too week to be satisfactory. This shows that the tripartite definition is incorrect. Suggestions on how to improve it have abunded. Consider the following example, taken from Theory of Knowledge Course.
A teacher has two students, Mr. Nogot and Mr. Havit, in her class. Mr. Nogot seems to be the proud owner of a Ferrari (a rare and expensive car). He says he owns one, drives one around, and has papers which state that the car he drives is his. However, he does not actually own a Ferrari.
The teacher, on the basis of this evidence, concludes that someone in her class owns a Ferrari. This is true enough, but only because Mr. Havit, who shows no signs of Ferrari ownership, secretly owns one. So, it seems that the three conditions (truth, belief and justification) of knowledge have been met, but that there is no knowledge.
Another example of a Gettier case can be developed from an example concerning whether an executive's secretary is in his office. Suppose that she looked into the office and saw, sitting behind the desk, a figure who looked to her exactly like her secretary. We may suppose that she would be completely justified in accepting that her secretary is in his office. However, it may be that the person sitting at the desk is her secretary's identical twin brother. The real secretary is hiding behind the desk, waiting to leap up and surprise her. So it is true that the secretary is in the office, the executive accepts that it is true, and she is completely justified in so accepting that he is.
A third example, very simple, is provided by a broken watch. Suppose it is 3.15 pm and that my watch stopped working yesterday exactly at 3.15 pm. Suppose that checking the time on my watch has always been a very reliable and hence strongly justification-affording procedure in the past. I wish to know what the time is and I check my watch. Do I know that it is 3.15 pm? Of course not, I am just extremely lucky, although the procedure followed is reliable by hypothesis, and my belief that it is 3.15 pm is true.
Gettier counterexample are easy to construct by maintaining but decoupling the justification of p from the truth of p. This can happen whenever p is, or refers to, an empirical (i.e. contingent) fact. In mathematical knowledge, where p is a theorem and its justification is a logical proof, not "Gettierisation" seems possible.
Luciano Floridi <firstname.lastname@example.org>
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