First, I took an acid trip. Then I asked scientists about the power of altered states.

A couple of decades ago, on a backpacking trip in the Sierra Nevada, I was marching up a mountain solo under the influence of LSD. Halfway to the top, I took a break near a scrubby tree pushing up through the rocky soil. Gulping water and catching my breath, I admired both its beauty and its resilience. Its twisty, weathered branches had endured by wresting moisture and nutrients from seemingly unwelcoming terrain, solving a puzzle beyond my reckoning. I sensed a kind of wisdom in its conservation of resources. I imagined that the tree somehow wanted me to learn its lessons, to slow down and save my strength for the rest of the climb.

Later, when I told the story to a friend, she noted that I talked about sitting “with” the tree. I’d anthropomorphized it, making the tree sound like an elder or a friend. Given that I became an atheist at the age of ten, and that I always found more comfort in science than any kind of spirituality, these feelings amused me. I know that humans see intention or purposeful design in many places where it doesn’t exist. We see Jesus in pieces of toast, yell at our laptops, concoct conspiracy theories, and say that everything happens for a reason. Psychologists say that humans have “hyperactive agency detection”; psychedelic drugs probably turn up the knob.

Still, over the years, I found myself thinking about that tree. This past February, the American Association for the Advancement of Science hosted a session called Learning Without Neurons, which examined memory in slime molds, electrical circuits, and materials that learn to self-fold in various ways in response to forces. In “The Soul of an Octopus,” the naturalist Sy Montgomery compares scuba diving among sea creatures to taking LSD. “I find myself in an altered state of consciousness, where the focus, range, and clarity of perception are dramatically changed,” she writes. In an e-mail, Montgomery told me that, while diving, she feels as if “the mental experience of one species is no more real or valuable than any other.” When I wrote about the biologist Michael Levin, who studies electrical signals that instruct cells to become body parts, he told me, “I look for cognition everywhere. In some places you don’t find it, but I think I see it broader than many people.” Maybe it does make sense to consider a tree’s intelligence.

A couple of years ago, I came across Diverse Intelligences, an initiative of the Templeton World Charity Foundation that funds research projects with names like “Brainless Intelligence” and “Play, a Computational Perspective.” (T.W.C.F. shares its founder with—and has received donations from—the John Templeton Foundation, an unusual funder of science and spirituality research that has made some scientists uneasy. In the words of one critic, “Templeton plies its enormous wealth with a single aim: to give credibility to religion by blurring its well-demarcated border with science.”) The idea of intelligence without a brain can sound mystical or speculative, but the initiative has attracted quite a lot of human intelligence—including Levin, who has appeared as a guest speaker—so I was intrigued. I applied to attend an online gathering of the Diverse Intelligences Summer Institute, which brings together scientists, philosophers, and artists interested in all forms of cognition…