I have elaborated the view – for both speaker meaning and word meaning, and for the vast bulk of expressions – that meaning consists in the expression of ideas, and that meaning is determined by the idea expressed. The word “dog” means something, for example, because it is conventionally used to express an idea. And it means “dog” rather than “cat” because it expresses the idea of a dog rather than the idea of a cat. A particular speaker means “dog” by a word when he or she uses it to express the idea of a dog. Hence the view that I have been developing is an ideational theory of meaning. I have acknowledged that for a relatively small set of expressions – interjections and the like – meaning consists in the expression of mental states other than ideas (see §2.5, §7.3). So, more generally, I have been developing a mentalistic theory of meaning. I have concentrated on words for which the relevant mental states are ideas, and shall continue to do so.

A major lacuna in classical ideational theories was that after the identification of meaning with the expression of ideas, little was said about expression. Yet without a detailed understanding of the relation of expression, the tautological character of formulas like “e means μ iff e expresses the idea μ” will wrongly suggest that ideational theories are vacuous.