Psychedelics are a class of drugs that radically alter consciousness and perception. Unlike heroin or cocaine, psychedelics such as LSD, mescaline, psilocybin, ibogaine, and dimethyltryptamine are neither physically harmful or habit-forming. Yet they are considered so frightening and dangerous that possession of them is punished by long prison sentences. Although they are thought to "expand consciousness," which sounds at least theoretically desirable, no sane adult can be allowed legal access to them.

The word psychedelic - "mind-manifesting" - was coined in the 1950s during our culture's brief enthusiasm for chemical self-discovery. In the mid-1960s, the substances were outlawed, and the mainstream vogue for consciousness expansion ended soon after. In the next decades, the media has repeatedly associated psychedelics with blown minds, wasted potential, and social chaos. The notion persists that to dabble in psychedelics, to trip, is to risk madness.

Among shamanic tribal cultures, plants that induce visions are the center of spiritual life and tradition. Tribes in Africa, Siberia, South and North America, and elsewhere believe that these plants are sentient beings, supernatural emissaries. They ascribe their music and medicine, their cosmology and extensive botanical knowledge to the visions given to them in psychedelic trance. For tribes in Africa, Siberia, North and South America, and many other regions, rejection of the visionary knowledge offered by the botanical world would be a form of insanity.

Many psychedelics are closely related to serotonin or other common neurotransmitters. Serotonin is believed to perform many functions. It helps to regulate sensory information - whether sense data trickles, flows, pours, or floods into the brain. Psilocybin, mescaline, and LSD are also alkaloids that resemble serotonin. The superpotent hallucinogen DMT ("NN - dimethyltryptamine") is a very close cousin to serotonin - the same molecular structure with the difference of two atoms. Serotonin Selective Re-uptake Inhibitors (SSRIs), such as the anti-depressants Prozac and Zoloft, limit mood swings by modulating the release of serotonin. Psychedelics bond to many of the same receptor sites as serotonin and similar neurotransmitters. That is the principle cause of their activity.

Think of the brain (as distinct from the mind) as a kind of radio. With "normative" levels of serotonin, the brain is tuned to "consensual reality" - something like the local Pop or Talk Radio station. By substituting psilocybin, Ibogaine, dimethyltryptamine, or some other psychedelic compound for serotonin and other neurotransmitters, you change the station and suddenly you begin to pick up the sensorial equivalent of avant-garde jazz, Tibetan chants, or another channel resonating with new and astonishing information. Yet your mind, the perceiving core of the self, remains more or less unaffected. In that sense, psychedelics - unlike alcohol or heroin - are not even intoxicating in an ordinary sense of the word.

Are psychedelics "good" or "evil"? In our culture these chemicals have been demonized, but like all profound and powerful tools, they are ambiguous. A computer can be an awesome educational instrument, or you can use it to play Doom fifteen hours a day. Psychedelics are different from other tools in one crucial respect: Because they work in the subjective domain of the individual's consciousness, the attitude one has before taking them shapes the effect they will have to an extraordinary degree. For this reason, laboratory conditions and the typical quantifying scientific method seem to be unsuitable for studying them.