We may sum up this theory of meaning in a simple formula. When through the law of conditioned reflexes, A has come to be a cause of C, we will call A an “associative” cause of C, and C an “associative” effect of A. We shall say that, to a given person, the word A, when he hears it, “means” C, if the associative effects of A are closely similar to those of C; and we shall say that the word A, when he utters it, “means” C, if the utterance of A is an associative effect of C, or of something previously associated with C. To put the matter more concretely, the word “Peter” means a certain person if the associated effects of hearing the word “Peter” are closely similar to those of seeing Peter, and the associative causes of uttering the word “Peter” are occurrences previously associated with Peter. Of course as our experience increases in complexity this simple schema becomes obscured and overlaid, but I think it remains fundamentally true. There is an interesting and valuable book by Messrs. C. K. Ogden and I. A. Richards, called _The Meaning of Meaning_. This book, owing to the fact that it concentrates on the causes of uttering words, not on the effects of hearing them, gives only half the above theory, and that in a somewhat incomplete form. It says that a word and its meaning have the same causes. I should distinguish between _active_ meaning, that of the man uttering the word, and _passive_ meaning, that of the man hearing the word. In active meaning the word is associatively caused by what it means or something associated with this; in passive meaning, the associative effects of the word are approximately the same as those of what it means.