Definitions as explications and the explanatory role of knowledge

What is a good definition of a philosophical or scientific concept? In this paper I will argue that definitions can fruitfully be seen as explications, essentially in the sense of the logical empiricism of Rudolf Carnap, whose mature view on the matter was detailed in a 1950 book on the logical foundations of probability (Carnap, 1950). Being an epistemologist, my example will be the concept of knowledge, but I believe that much of what I say about definitions applies to other concepts as well. The second part of this paper is more specifically epistemological: it concerns the prospects of subsuming various approaches to epistemology under a methodology which relies on Carnap's method of explication—in particular, on approaches that emphasize the explanatory role of knowledge. Hence, in a sense, this paper develops a metatheory of epistemology—a theory of the theory of knowledge.