Publisher Summary A metaphor is treated as the merely ornamental comparison of similars. The comparison theory, though implying a more active mode of cognition than the simple substitution theory, fails to identify the most interesting sorts of metaphors. If a metaphor is just comparison, then the content of scientific assertions involving a metaphor will be confined to material concerning the realms of actual and possible experience, as comparisons are essentially rooted in experience. But most sciences are, for reasons that develop, inclined to include assertions about those features of the world that are beyond all possible experience. A metaphor is a figure of speech; a model is a non-linguistic analog. An object or state of affairs is said to be a model when it is viewed in terms of its relationship to some other object or state of affairs. There is, however, one role that a metaphor performs and a simile, precisely by virtue of its grammatical form, cannot. This is to supply a term where one is lacking in the vocabulary, the process of catachresis. What are often referred to as the “theories of metaphor” are for the most part theories as to the nature of the transfer or the comparison that a metaphor effects. They are theories of the way in which metaphors provide, in Dr. Johnson's words: two ideas for one. Max Black has been the main philosophical exponent of Richards' ideas, proposing in an early article, Metaphor, what he has called the “interactive view of metaphor.” Black's contention is that each metaphor has two distinct subjects—principle and subsidiary—and the principal subject acquires new meaning through its involvement with the subsidiary one.