Robert Frost's biographer describes him as a man of contradictions. On the one hand he was an individualist who wanted to do things his way; on...

In one sense, the biographer's statement is a sort of cliché that every biographer succumbs to when building a complex portrait of his/her subject. It is a device meant to fend off any criticism from readers who find incidents in the subject's life that contradict the author's main view.  If I said "Einstein was an intelligent man" someone would  point out that several of his life choices were unwise, so I say "Einstein was a man of contradictions."

  In this particular case, however, the poem itself is about choice, and about the contradictions that are built into any decision.  If the biographer feels that somewhere in his career Frost "chose the path" of "fitting in" or the choice of "doing things his own way," then the poem could be seen as his statement about his doubts or ponderings about what would have been if he had made the other choice.  The analogy breaks down once  one path is chosen over the other, since the biographer is saying that Frost somehow "walked" both paths.