This paper addresses the following questions: (a) what did Locke mean when he said that \u27words signify ideas\u27? and (b) what is Locke\u27s argument for this thesis, and how successful is it? The paper argues that the two most prominent interpretations, those of Norman Kretzmann and E. J. Ashworth, attribute to Locke an argument for his semantic thesis that is fallacious, and that neither can make good sense of two key passages in book 3 of the Essay concerning Human Understanding. An alternative understanding of signification, drawn from the works of Hobbes and the Port-Royal logicians, is explored and shown to provide both a satisfactory interpretation of these two passages and an understanding of Locke\u27s argument for the thesis th...