The main point of this paper is logical in character. We intend to offer an explication of the term ”sign” — which, to be sure, is merely one of the indefinitely many possible explications of the term’s meaning — and to consider, in part II, several of its consequences for the semiotics of art. Hence, we will not try to settle any substantive issues in semiotics directly or construct a particular theory of signs (or a part of such a theory) in order to pit it against other theories in the field; nor are we going to describe the results of empirical semiotic research based on some such theory. We will merely give a more rigorous expression to some theoretical intuitions, mostly those concerning the notion of sign, by explicating them in terms of more precise concepts. Naturally, to explicate an intuition is not only to report or articulate it, but also to make it precise, retain some of its elements while discarding the others, and to reconstruct it.