That personhood is, above all else, authentic. “Two roads diverged in a wood, and I— / I took the one less traveled by”: The claim here, according to the poem’s popular interpretation, is that the speaker took the more arduous spiritual and personal journey. This is also, not at all coincidentally, the path to the truest version of the speaker’s self, according to most models of self-improvement. Indeed, if “The Road Not Taken” can serve as a metaphor for thirty years of behavioral economics, psychology, and neuroscience, it is at least equally emblematic of the half-century-old self-help movement, as its popularity in motivational posters can attest.

This is in part traceable to a single book. In 1978, M. Scott Peck published The Road Less Traveled: A New Psychology of Love, Traditional Values and Spiritual Growth, a guide to reforming oneself that drew heavily on Peck’s career as a psychiatrist and his somewhat unconventional religious views. (His final book, published in 2005, was a memoir about exorcisms.) The Road Less Traveled languished for several years, but by the early eighties, word of mouth and Peck’s assiduous courting of reviewers had turned it into one of the foundational texts of modern self-help. In a 2012 article, the Christian Science Monitor declared it to be among the ten greatest self-improvement books ever written (placing it in company with those of Benjamin Franklin and Dale Carnegie), and according to Peck’s website, The Road Less Traveled “has sold over 7 million copies and remained on the New York Times Best Seller List longer than any other paperback book.” As with many self-help guides, the book itself is a kind of olive loaf composed of corn-fed common sense (“The process of listening to children differs depending on the age of the child”) liberally seasoned with nuggets of kookiness (“Moreover, were I ever to have a case in which I concluded after careful and judicious consideration that my patient’s spiritual growth would be substantially furthered by our having sexual relations, I would proceed to have them”).

Outside of its title, The Road Less Traveled never mentions the poem from which it takes its name. But Peck’s reading of Frost is probably even stronger for being implicit. “Life is difficult,” begins The Road Less Traveled, and you can tell Peck means it, because he gives those three words their very own paragraph. What we need to learn, he goes on to argue, is self-discipline. This will allow us to see that “the fact that life is difficult no longer matters.” Later, we will discover that in order to follow “the road of spiritual growth,” we must “begin by distrusting what we already believe, by actively seeking the threatening and unfamiliar.” The book is essentially a three-hundred-page elaboration of the message most people attribute to “The Road Not Taken”: Life is a hard, lonely, but ultimately triumphant struggle.