A. J. Ayer argues that the necessary and sufficient conditions for S knowing that p are:
(1) p is true.
(2) S is sure that p.
(3) S has the right to be sure that p.
STEP 1: Ayer begins by noting that it is not a sufficient condition for S to know that p that (i) S is sure that p, and (ii) p is true. The source of S’s belief that p must be generally reliable.
Example: A superstitious person who is sure that he will suffer misfortune for walking under a ladder, who happens to be right, still does not know that he will suffer misfortune. This is because his superstitious belief about ladders is not generally reliable.
Upshot: S knows that p only if her belief that p is formed via a generally reliable process (of reasoning).
STEP 2: Ayer considers whether we can arrive at the standards of knowledge by determining what would be a satisfactory answer to the question: How do you know? He opines that one’s answer to this question is only satisfactory if the source of knowledge is reliable in the particular case.
Examples: If my eyesight is bad or my memory is poor, they may fail to provide an adequate basis for knowledge, even if I turn out to be right. However, attempting to list the conditions under which perception, memory, testimony etc. are reliable may be a moribund affair.
Upshot: Determining if S’s belief is formed via a reliable process may have to be determined on a case by case basis.
STEP 3: Ayer suggests that reliability may be sufficient for knowledge even when an answer to the question, “How do you know?” is not available. The most salient question seems to be whether or not one has the right to be sure.
Example: A man who is reliable at predicting lottery results may be credited with knowledge if his run of success is sufficiently impressive.
Upshot: Whether S knows that p depends, not on her inner states or on whether she arrived at her belief by an accredited route to knowledge, but on whether S is reliable enough for us to concede that she has the right to be sure.
STEP 4: Ayer suggests that debates about whether or not it possible to know that p are actually debates about whether or not one ever has the right to be sure that p.
Example: The sceptic about knowledge is not trying to get us to revise the meaning or use of the verb “to know” but rather is denying that we have the right to be sure.
Upshot: Arriving at a definition of knowledge does not settle the question of whether it possible to have it since whether or not we have the right to be sure remains open to debate.
The central problem confronting contemporary epistemologist is not trying to figure out the necessary and sufficient conditions for knowledge, but rather trying to determine if and when one necessary condition in particular has been met; namely, if and when we have the right to be sure.
By Ayer’s lights, who decides if S has the right to be sure that p? Do you agree? Why or why not?