What is ambiguity? Under what conditions is a word ambiguous? We all claim a certain practical facility in spotting ambiguities, but the theory of the matter is in a sorry state. Logicians and philosophers typically concern themselves with ambiguity either as a defect in the arguments of others or as a hazard from which their own serious discourse is to be protected. Literary critics, alive to the rhetorical values of ambiguous expression, are not equally sensitive to the philosophical demands for clarity and system. General analytical questions thus remain for the most part unexplored, while commonly repeated explanations suffer from various grave difficulties.

A word is, for example, said to be ambiguous if it has different meanings or senses, or if it stands for different ideas. But ghostly entities such as meanings, senses, or ideas provide no more than the ghost of an explanation unless, as seems unlikely, they can be clearly construed as countable things whose relations to one another and to words are independently determinable. At best, such entities may be regarded as hypostatizations of the content of sets of synonymous expressions, the specification resting on the critically obscure notion of synonymy.