From 1949 to 1966, the pharmaceutical company Sandoz dispensed free amounts of “however much LSD any researcher requested” to conduct trials. In 1957, before Leary had even tripped for the first time, R. Gordon Wasson, a New York banker, published a lengthy essay in the far-from-radical Life magazine about taking mushrooms in Mexico.

Image Michael Pollan Credit... Jeannette Montgomery Barron

In Mexico and elsewhere, experiences with naturally occurring hallucinogens predated Hofmann’s discovery of LSD by a long, long time. The wonderfully named but factually dubious “stoned ape theory” posits that great evolutionary leaps were made when early humans ingested psilocybin. It’s unlikely that tripping led directly to, say, the development of language, as some proponents of that theory claim. But more convincing conjectures include the one Wasson made about mushrooms in Life: “One is emboldened to the point of asking whether they may not have planted in primitive man the very idea of a God.”

Like many who claim to encounter the divine, trippers often come back with knowledge comically difficult to convey. Plenty of testimonies cited in “How to Change Your Mind” are nontransferable mental checks. “I became the music for a while,” one person recounts after a trip. Another: “I don’t know why he’s yellow and lives in my left shoulder.” And Pollan himself: “It suddenly dawned on me that these trees were — obviously! — my parents.”

You get the point(lessness). But unlike people drunk or high who feel compelled the next day to shake their heads at what they did or thought under the influence, psychedelic users often feel the opposite, as if it’s important to keep a foot in the place they were while gone. They might not credit the man in their shoulder, but their philosophical revelations about self and relationships and need and perspective last longer than you might expect. Pollan writes: “The traces these experiences inscribed remain indelible and accessible.” William James, whose openness to mystery makes him one of the guiding lights of Pollan’s book, once wrote of the substantial aftermath of mystical experiences: “Dreams cannot stand this test.”

In all of this is an assumption that the true value of psychedelics is not the experience of them — the grooviness of the moment — but the sediment the experience leaves behind.

It’s possible these effects can be chalked up, in part, to the drug’s effect on the brain’s so-called default mode network, especially the part associated with self-referential thought. Pollan grants, if briefly, that turning off the network — truly getting over yourself — might also be achieved through “certain breathing exercises,” or through “sensory deprivation, fasting, prayer, overwhelming experiences of awe, extreme sports, near-death experiences and so on.”

Pollan doesn’t give a lot of prime real estate to psychedelics’ naysayers. But given that those on LSD can appear to be losing their minds, and that the drug leaves one feeling emotionally undefended (a potential benefit as well as a profound risk), he does strongly recommend having an experienced guide in a proper setting when you trip. With those safeguards in place, he believes usage could be on the verge of more widespread acceptance, pointing out that plenty of other once widely derided practices redolent of the ’60s, like yoga and natural birth, are now common.