Metaphors can be based on similarities

"Metaphors can be based on similarities, though in many cases these similarities are themselves based on conventional metaphors that are not based on similarities. Similarities based on conventional metaphors are nonetheless real in our culture, since conventional metaphors partly define what we find real." (#60 2660)

"Though the metaphor may be based partly on isolated similarities, we see the important similarities as those created by the metaphor, as described above." (#60 2663)

"The primary function of metaphor is to provide a partial understanding of one kind of experience in terms of another kind of experience. This may involve preexisting isolated similarities, the creation of new similarities, and more." (#60 2666)