Preliminary to setting out several formal meanings of “specific etiology” and related concepts, some general statements of a semiphilosophical sort may be in order. Space limitations prohibit a systematic defense of these points, which I shall therefore make succinctly and, in appearance but not by intent, perhaps rather dogmatically, referring the reader to other writings of mine on this and related topics (Meehl, 1973b, especially chaps. 1, 5, 11-13).