In this paper, I shall try to enhance our understanding of Aristotle’s thought by relating it to certain contemporary problems and insights of philosophical logicians. Now one of the most central current issues in philosophical logic is a challenge to a hundred-year old dogma. Almost all twentieth-century philosophers in English-speaking countries have followed Frege and Russell and claimed that the words for being in natural languages — “is”, “ist”, έστι, etc. — are ambiguous between the is of predication, the is of existence, the is of identity, and the generic is. The significance of this ambiguity thesis has not been limited to topical discussions but has extended to historical studies, including studies of ancient Greek philosophy. A generation or two of scholars working in this area used the Frege — Russell ambiguity thesis as an important ingredient of their interpretational framework. Cases in point are Cornford, Ross, Guthrie, Cherniss, Vlastos, Ryle, and (from the German-language area) Heinrich Maier. Indeed, the Frege — Russell distinction is still being invoked occasionally by Aristotelian scholars; see e.g., Moravcsik (1967, p. 127), Kirwan (pp. 100–101, 141), Weidemann (1980, p. 78) and Gomez-Lobo (1980–81, p. 79).