What exactly is mysticism? One of the problems with defining and evaluating mysticism is that mystical experiences seem to be inherently personal and unobservable to outsiders. Certainly, one can observe a person meditate and then record what that person says about his or her experience while meditating, but what is real about that experience? Persons undergoing such experiences often describe a feeling of oneness with the universe, love for all creation, and communion with the divine. But anyone can dream or daydream or imagine. It would be one thing if mystics came up with great ideas during their meditative states — a cure for a disease, a viable plan for peace between warring states, or a better political system. But this generally does not happen. Mystical experiences remain personal.

Recently, however, brain scan technologies, along with knowledge of the different functional areas of the human brain, have allowed scientists for the first time to actually observe what is going on in the brains of people who are undergoing mystical experiences. And the findings are remarkable.

Studies of persons engaged in prayer or meditation indicate that the frontal lobes of participants’ brains, responsible for concentration, light up during meditation– an unsurprising conclusion. However, at the same time, the parietal lobes of the same brains go dark — these sections of the brain are responsible for an individual’s sense of self, and help a person orient him or herself to the world. So when a person claims that they experience a oneness with the universe, that appears to be exactly what is going on — the person’s sense of self is actually put to sleep. And when the sense of self disappears, so does egocentrism. Researchers have found that people who regularly engage in meditation literally reshape their brains, becoming both more attentive and compassionate. The particular religion they belong to did not matter — Buddhist, Christian, Sikh — all seemed to experience the same changes in the brain.

Research on psychedelic drugs has found evidence that psychedelics act as potent enablers of mystical experience. Psilocybin, the active chemical in “magic mushrooms,” and mescaline, from the cactus known as peyote, are psychedelics that have been used for thousands of years in Native American religious ceremonies. LSD was synthesized in 1938 from a fungus, ergot, that may have played a role as a hallucinogen in ancient Greek religions. What these chemicals have in common is that they all seem to have effects on the brain similar to what may be experienced during deep meditation: they dissolve the sense of self and enable extraordinary visions that appear to give people a radically new perspective on their lives. One research subject described her experience on psilocybin as follows: “I know that I had a merging with what I call oneness. . . . There was a time that I was being gently pulled into it, and I saw it as light. . . . It isn’t even describable. It’s not just light; it’s love.” In fact, two-thirds of study participants who received psilocybin ranked their psychedelic experience as being among the top five most spiritually significant experiences of their lives, comparable to the birth of a child or the death of a parent.

Psilocybin has even been used to treat addiction — the mystical experience seems to reboot the brain, allowing people to break old, ingrained habits. A study of fifteen smokers who had failed multiple treatments for addiction found that after therapy sessions with psilocybin, 80 percent were able to quit cigarettes for at least 6 months, an unprecedented success rate. Smokers who seemed to have a more complete mystical experience had the greatest success quitting. According to one subject, “smoking seemed irrelevant, so I stopped.” Cancer patients who underwent treatment with psilocybin had a reduction in anxiety and distress.

Brain scans of those undergoing mystical experiences under psychedelics indicate reduced activity in the part of the brain known as the “default-mode network.” This high-level part of the brain acts as something of a corporate executive for the brain. It inhibits lower-level brain functions such as emotion and memory and also creates a sense of self, enabling persons to distinguish themselves from other people and from the rest of the world. When psychedelics suppress the default-mode network, the lower brain regions are unleashed, leading to visions that may be bizarre but, in many cases, insightful. And the sense of self disappears, as one feels a merging with the rest of the world.

It’s important not to overstate the findings of these scientific studies, by citing spiritual experiences as justification for theism. These studies do not prove that God exists or that there is a supernatural dimension. The visions that people experience while under psychedelics are often chaotic and meaningless. But this sort of radical free association does seem to help people attain new perspectives and enhance their openness to new ideas. And the feeling of oneness with the universe, the dissolution of the self, is not just an unconfirmed claim — it really does seem to be supported by brain scan studies. So the mystical experience is not superstitious pre-scientific thinking, but a valid mode of thought, one which many of us, including myself, have dismissed without even trying.