can distinguish, identify, and categorize more subtle differences. For instance, the wine taster who can distinguish micro-differences in taste, body, and bouquet is more knowledgeable than he who finds little difference between Gallo, Mogen David, and Harvey's Bristol Cream.
From this kind of elementary analysis Ayer goes on to examine other possibilities--for instance, Does knowing consist of being in a special state of mind?--and concludes that knowing involves "having the right to be sure." That is, the necessary and sufficient conditions of knowing or having knowledge are that (1) what is known must be true, (2) the knower must be sure of what he knows, and (3) the knower must have adequate evidence to demonstrate that what he surely knows is true.
With such a conclusion as this Ayer subtly but clearly reformulates the definition of the problem of knowledge; the question "can we know" is now seen not to be dependent upon the discovery of what knowledge "is," but dependent upon the kind(s) of justification adduced in support of surety -- on the evidence. Put otherwise, the problem of knowledge is not "What is Knowledge?" but "How can we use the verb to know with assurance?" Thus the question of evidence is central to the satisfactory formulation of a theory of knowledge yet, even so, the criteria of satisfactory evidence must not be built into the theory. In Ayer's terms,
This right [to be sure] may be earned in various ways; but even if one could give a complete description of them it would be a mistake to try to build it into the definition of knowledge, just as it would be a mistake to try to incorporate our actual standards of goodness into a definition of good.
The answer to the "meta-epistemological" question, "how do you know you know?," is thus left open--in this essay at least. An approach to the entire problem is found in the book from which this essay is taken, as well as Ayer earlier work, Language, Truth, and Logic.
A. J. Ayer
It is by its methods rather than its subject-matter that philosophy is to be distinguished from other arts or sciences. Philosophers make statements which are intended to be true, and they commonly rely on argument both to support their own theories and to refute the theories of others; but the arguments which they use are of a____________________