To a considerable extent Pollan approaches the subject by describing his encounters with people who have been involved in this renaissance. But he has also tried out some of the substances; he describes his experiences and reflects on what, if anything, psychedelic phenomena tell us about the widespread claims made for them as a gateway to 'spiritual' knowledge and awareness. This in turn relates to another idea, also favoured by Huxley, of the Perennial Philosophy: the notion that mystical experience derives from a fundamental capacity of human nature that is the basis of all religions.
Such claims are probably the main reason that psychedelics have such fascination for many people. As Pollan discovered, several researchers who began by approaching the subject from a detached scientific standpoint found themselves being increasingly drawn towards the mystical position. His own attitude is somewhat ambivalent.
How are we to evaluate the "insights" these people bring back from their psychedelic journeys? What sort of authority should we grant them? Where in the world does the material that makes up these waking dreams or, as one volunteer put it, "intrapsychic movies", come from? The unconscious? From the suggestions of their guides and the setting of the experiments? Or, as many of the volunteers believe, from somewhere "out there" or "beyond"? What do these altered states of consciousness ultimately mean for our understanding of either the human mind or the universe?A related idea, which goes back at least as far as William James in The Varieties of Religious Experience at the start of the twentieth century, is that the brain doesn't generate consciousness but rather is a filter that narrows the wide spectrum of "cosmic consciousness" to a manageable proportion, thus allowing us to act effectively in the world. Pollan has a chapter saying that how the drugs work on the brain may be relevant to this way of thinking.
In at least some cases investigators have approached psychedelics from a prior philosophical position that coloured their conclusions. A case in point is Robert Gordon Wasson, the amateur mycologist who "rediscovered" the psilocybin mushroom, which had been used in sacred rituals in Central and South America until these were suppressed by the Spanish after the conquest.
In 1955 Wasson managed to persuade Maria Sabina, a 'wise woman' or curandera in Mexico, to allow him to take part in a traditional ceremony in which the mushrooms were used. From their effects on him he concluded that they confirmed the truth of his theory that such mushrooms were the source of all religion. This was not how Maria herself understood the use of the mushrooms—she saw them as a means of healing—but in any case her decision to allow Wasson to participate was a mistake. After he published an article describing his experience in Life magazine there was a huge influx of visitors, including Bob Dylan, John Lennon, and Mick Jagger, who swamped the village; the once secret mushrooms were now sold openly in the street. Maria's neighbours blamed her; her house was burned down and she was briefly imprisoned.
A feature of the revival of interest in psychedelics has been their use to treat anxiety and depression in the terminally ill and also addictions, including smoking. So far the results have been promising and Pollan includes an impressive case history, but the numbers are still too small to allow firm conclusions. The clinicians involved in these trials appear to have little interest in metaphysical questions about the patients' experiences.
This book contains a lot of interesting information but could have done with pruning. I found the historical material and the biographical accounts of the researchers to be over-long and too detailed, and the same applies to the descriptions of volunteers' experiences; I've read so many of these over the years that they are beginning to lose their interest for me.
On the other hand, I should have like to read more about the wider resonances of these things. For example, it would have been worth mentioning David Lewis-Williams's theory that the upper palaeolithic cave paintings were made under the influence of hallucinogens (see The Mind in the Cave and Conceiving God). Another echo comes from the study of shamanism; shamanic experiences sound remarkably similar to those reported in the modern psychedelic literature (which is hardly surprising since they were probably produced in a similar way).
Incidentally, it's curious that some modern scholars of shamanism, such as Ronald Hutton, Ioan M. Lewis and Piers Vitebsky, seem to have an equivocal attitude to the 'reality' of the phenomena they describe that is similar to what one finds in some researchers on psychedelics.
Finally, for anyone wanting to read more on these themes, I'd recommend Marghanita Laski's Ecstasy and John Horgan's Rational Mysticism.