Two distinct objects may, by being dexterously presented, again and again in quick succession, to the mind of a cursory reader, be so associated together in his thoughts, as to be conceived capable . . . of being actually combined in practice. The fallacious belief thus induced bears a striking resemblance to the optical illusion effected by that ingenious and philosophical toy called the Thaumatrope; in which two objects painted on opposite sides of a card,—for instance a man, and a horse,—a bird, and a cage,—are, by a quick rotatory motion, made to impress the eye in combination, so as to form one picture, of the man on the horse’s back, the bird in the cage, etc.

What is fallacious in an argument can be mesmerizing in a poem. “The Road Not Taken” acts as a kind of thaumatrope, rotating its two opposed visions so that they seem at times to merge. And that merging is produced not by a careful blending of the two—a union—but by “rapid and frequent transition,” as Whately puts it. The title itself is a small but potent engine that drives us first toward one untaken road and then immediately back to the other, producing a vision in which we appear somehow on both roads, or neither.

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THAT SENSE OF MOVEMENT is critical to the manner in which the poem unfolds. We are continually being “reset” as we move through the stanzas, with the poem pivoting from one reading to the other so quickly that it’s easy to miss the transitions. This is true even of its first line. Here’s how the poem begins:

Two roads diverged in a yellow wood,

And sorry I could not travel both

And be one traveler, long I stood

And looked down one as far as I could

To where it bent in the undergrowth . . .

The most significant word in the stanza—and perhaps the most overlooked yet essential word in the poem—is “roads.” Frost could, after all, have said two “paths” or “trails” or “tracks” and conveyed nearly the same concept. Yet, as the scholar George Monteiro observes:

Frost seems to have deliberately chosen the word “roads.” . . . In fact, on one occasion when he was asked to recite his famous poem, “Two paths diverged in a yellow wood,” Frost reacted with such feeling—“Two roads!”—that the transcription of his reply made it necessary both to italicize the word “roads” and to follow it with an exclamation point. Frost recited the poem all right, but, as his friend remembered, “he didn’t let me get away with ‘two paths!’”