"I doubt if any thing is more related to another thing than it is to any third thing except as we make it," Robert Frost wrote in his notebooks, as quoted by Adam Kirsch in his review, "Subterranean Frost." Kirsch comments that here, Frost "shows how the power of metaphor can turn on the poet, plunging him into a world of sheer perspectivism where there is no essence, only likeness."
When I wrote my essay on "The Mountain," I was quite surprised by my conclusion that the poem "acts out how poetry creates the contrast between nature and culture it purports to dissect." Though I once read all of Frost through (when I got the Library of America edition), I had not understood his work in such basically Nietzschean terms at all. But given the passage Kirsch quotes, it appears that I was on the right track: in Frost (and not only in his work but apparently for him as a person, too), the relations established by metaphor (or simile, in "The Mountain") create the contrasts with which we understand the world.
(Nietzsche: I'm thinking of "Über Wahrheit und Lüge im außermoralischen Sinne" in particular; an English version is here.)