problem of the criterion a problem of epistemology, arising in the attempt both to formulate the criteria and to determine the extent of knowledge. Skeptical and non-skeptical philosophers disagree as to what, or how much, we know. Do we have knowledge of the external world, other minds, the past, and the future? Any answer depends on what the correct criteria of knowledge are. The problem is generated by the seeming plausibility of the following two propositions: (1) In order to recognize instances, and thus to determine the extent, of knowledge, we must know the criteria for it. (2) In order to know the criteria for knowledge (i.e., to distinguish between correct and incorrect criteria), we must already be able to recognize its instances. According to an argument of ancient Greek Skepticism, we can know neither the extent nor the criteria of knowledge because (1) and (2) are both true. There are, however, three further possibilities. First, it might be that (2) is true but (1) false: we can recognize instances of knowledge even if we do not know the criteria of knowledge. Second, it might be that (1) is true but (2) false: we can identify the criteria of knowledge without prior recognition of its instances. Finally, it might be that both (1) and (2) are false. We can know the extent of knowledge without knowing criteria, and vice versa. Chisholm, who has devoted particular attention to this problem, calls the first of these options particularism, and the second methodism. Hume, a skeptic about the extent of empirical knowledge, was a methodist. Reid and Moore were particularists; they rejected Hume’s skepticism on the ground that it turns obvious cases of knowledge into cases of ignorance. Chisholm advocates particularism because he believes that, unless one knows to begin with what ought to count as an instance of knowledge, any choice of a criterion is ungrounded and thus arbitrary. Methodists turn this argument around: they reject as dogmatic any identification of instances of knowledge not based on a criterion. See also SKEPTICIS. M.St.