Aristotle illustrates his view of the relation of metaphor to simile as follows. "When the poet say of Achilles, 'He sprang on them like a lion,' this is a simile. When he says, 'The lion sprang on them,' this is metaphor; for as both animals are brave, he has transferred the name of 'lion' to Achilles." Elsewhere he calls simile "a metaphor with a preface" and declares it inferior to metaphor on two counts: it is lengthier, therefore less pleasing; and "since it does not affirm that this is that, the mind does not inquire into the matter." Now it is true that metaphor is often (not, I think, always) preferable to simile on both these grounds, but the grounds are rhetorical not semantic ones. Terseness is more pleasing and more stimulating to thought than verbosity; that is what it comes to.