
At first, this problem was somewhat hard to pinpoint, but after reading the following example on Gettier’s own Wikipage I get it (not proven).
I am watching the men’s Wimbledon Final, and John McEnroe is playing Jimmy Connors, it is match point, and McEnroe wins. I say to myself: “John McEnroe is this year’s men’s champion at Wimbledon”. Unbeknownst to me, however, the BBC were experiencing a broadcasting fault and so had broadcast a tape of last year’s final, when McEnroe also beat Connors. I had been watching last year’s Wimbledon final, so I believed that McEnroe had bested Connors. But at that same time, in real life, McEnroe was repeating last year’s victory and besting Connors! So my belief that McEnroe bested Connors to become this year’s Wimbledon champion is true, and I had good reason to believe so (my belief was justified) — and yet, there is a sense in which I could not really have claimed to “know” that McEnroe had bested Connors because I was only accidentally right that McEnroe beat Connors — my belief was not based on the right kind of justification.
A Priori Justification and Knowledge (SEP)
A priori justification is a type of epistemic justification that is, in some sense, independent of experience. Gettier examples have led most philosophers to think that having a justified true belief is not sufficient for knowledge and the examples there), but many still believe that it is necessary. In this entry, it will be assumed, for the most part, that even though justification is not sufficient for knowledge it is necessary and that a priori knowledge is knowledge based on a priori justification. So much of the discussion will focus on a priori justification.
There are a variety of views about whether a priori justification requires some sort of evidence or whether, instead, some propositions can be “default reasonable”, or that a person can be entitled to accept certain propositions independent of any evidence, perhaps because they are reasonable presuppositions of some area of inquiry. Philosophers who think that a priori justification requires evidence differ about the details. Some think that a priori evidence can be defeated (overridden or undercut) by other evidence, including evidence from sensory observations. There are a variety of views about whether a priori justification, and knowledge, must be only of propositions about what is possible or necessary, and if necessary, only of analytic propositions, that is, propositions that are in some sense “true in virtue of their meaning”. Those who think that a priori justification requires evidence often think that the evidence is provided by rational intuitions or insights, but there is disagreement about the nature of those intuitions or insights, and critics deny that they really do constitute evidence.
Read the rest here: https://plato.stanford.edu/entries/apriori/














