Seventy years ago, men of first-rate ability described the transcendental experiences which come to those who, in good health, under proper conditions and in the right spirit, take the drug. How many philosophers, how many theologians, how many professional educators have had the curiosity to open this Door in the Wall?

The answer, for all practical purposes, is, None. In a world where education is predominantly verbal, highly educated people find it all but impossible to pay serious attention to anything but words and notions.

Writing in The Doors of Perception in 1954, Aldous Huxley lamented seven lost decades across which the ‘Pharisees of verbal orthodoxy’ had refused to take much serious interest in the astounding properties of the peyote cactus. The German pharmacologist Ludwig Lewin brought those properties to scientific attention in the mid-1880s. What Huxley described as the ‘active principle’ was isolated and given the name ‘mescaline’ a decade later.

Another 70 years on from the publication of The Doors of Perception, and a sense of wasted time once again hangs heavy over those who are interested in the potential of such psychedelics.

Huxley was involved, in the mid-1950s, with plans for a project called ‘Outsight’. It would have funded a group of between 50 and 100 prominent intellectuals – Graham Greene, Carl Jung and Albert Einstein among them – to take mescaline and record their reflections.

Outsight would, it was hoped, set psychedelics research on a firm, respectable footing. The required funding, however, never came through. Within little more than a decade psychedelics had become associated instead with the likes of Timothy Leary: a pioneering individual, no doubt, but a man whose antics, politics and influence over the counter-culture generation of the 1960s helped to push psychedelics to the social margins in the United States and around the world.

Since the early 2000s, that picture has been changing and the therapeutic potential of psilocybin in particular is being explored in a range of major studies. There is cautious hope that we may be on the verge of new forms of treatment for depression in particular.

Huxley’s The Doors of Perception retains enormous relevance for the world that we may now be entering: one not just of psychedelic therapeutics, but psychedelics used in religious and spiritual communities and retreats.

Aldous Huxley came to psychedelics late in life. He was not far off 60 at the time of his first ‘trip’ in May 1953, by which time he was committed to the idea that human beings are capable of knowing the ‘Divine Ground’, from where, he claimed, the everyday world of people and planets is derived. Such knowledge, he suggested, based on a study of mystical traditions the world over, was of a unitive rather than a cognitive kind. It was a form of knowing by participation and identity rather than the sort of knowledge that can be captured and communicated in words.

The prospect of unitive knowledge was deeply consoling for Huxley, since it promised an experience of a deeper self beyond the ordinary one, with all its everyday anxieties, frustrations and disappointments. The idea was also politically vital, as far as Huxley was concerned. He wrote his book on the subject, The Perennial Philosophy (1945), against the backdrop of a catastrophic world war and – as he saw it – the degeneration of the human religious impulse into the mass delusions and devotions of fascism. The only credible prospect for peace after this war, he thought – and he was far from alone in this – was to somehow find common ground for disparate traditions of thought and worship around the world – to create an outlet for people’s desire for self-transcendence that would inspire harmony and co-operation rather than conflict.

For Huxley, who was interested in Asian traditions, including Hinduism and Buddhism, the answer lay in an experience of the Divine that lay beyond doctrines and institutions. From India’s Upanishads to medieval Europe’s Meister Eckhart, he became convinced that the world’s mystical literature attested to the reality of this experience.

How, though, was someone as stiff and English and intellectual as Huxley to gain this precious experience? How, as he put it, ‘can we ever visit the worlds which to Blake, to Swedenborg, to Johann Sebastian Bach, were home?’

Living and working at this point in the United States, Huxley practised meditation and did his best – despite the temptations of having Hollywood starlets in his midst – to live the sort of loving and self-forgetful life that was both a good in itself and tended, it was said, towards fostering mystical states. He also wondered whether hypnosis or autohypnosis might help.

In the end it was a single pill, 400 mg of mescaline, that brought Huxley home. There were no Blakean visions, but rather an extraordinary experience of ‘reality’ as Huxley supposed it must be. A simple vase of flowers on the table was transfigured into ‘what Adam had seen on the morning of his creation – the miracle, moment by moment, of naked existence’. As the ‘throttling embrace’ of his ordinary ‘I’ was removed, the books on Huxley’s shelves glowed like precious stones – not just vividly-hued, but also communicating a sense of profound meaning.

Huxley subscribed to the filter theory of consciousness, whereby the survival of the animal requires that a great deal about the world be held at bay – filtered out from that animal’s awareness – while the business of eating, escaping trouble and procreating is conducted. That which makes it past this ‘reducing valve’ is, wrote Huxley, duly ‘consecrated as genuinely real by the local language’.

Huxley discovered during his trip why art and music are so highly prized in human cultures: they move us towards this unfiltered apprehension of the Divine. They don’t, however, take us all the way, Huxley concluded – having had his attention drawn to a simple chair during his trip and then shortly afterwards encountering Van Gogh’s Chair in a book on art. Of the chair that Huxley saw, he wrote:

The legs, for example… how miraculous their tubularity, how supernatural their polished smoothness! I spent several minutes – or was it several centuries? – not merely gazing at those bamboo legs, but actually being them – or rather being myself in them; or, to be still more accurate (for ‘I’ was not involved in the case, nor in a certain sense were ‘they’) being my Not-self in the Not-self which was the chair.

Van Gogh’s chair, by contrast, was ‘incomparably more real than the chair of ordinary perception’, but its genius as a piece of art lay in its ability to serve as a symbol for a chair experienced in its ‘Suchness’, as Huxley felt he had done during his hours on mescaline. Symbols, he wrote, ‘can never be the things they stand for’.

This last observation helps to explain why what some are calling a ‘psychedelic renaissance’ has been so long in coming. Most obviously, the outlawing of these substances around much of the world from the late 1960s onwards and their association in people’s minds with recreational self-indulgence alongside psychological and social harm, were what stymied research into psychedelics and their potential applications.

Yet those who Huxley described as ‘Pharisees of verbal orthodoxy’ also bear some of the responsibility: encouraging not just a faith in what words can do but also a profound uneasiness about the possibility of a world – or worlds – beyond that which words can capture. Huxley had great interest in and respect for the natural sciences, but he was among those who felt frustration at the equivalence between that which the natural sciences take as their object of study – the material world – and the full extent of what there is.

Huxley is not short of kindred spirits today. Jeffrey Kripal, a professor at Rice University in Texas and chair of trustees at the Esalen Institute in California – whose mission to offer an alternative humanistic education Huxley inspired – has written about the need for what he calls ‘the flip’: a moment in a person’s life when they are shaken out of habits of thought that lead them to explain everything in their experience in terms of a purely physical universe. For Huxley, too, an automatic explanatory appeal to what he called a ‘Freudo-Physicalist’ view of the world had been one of the great conceits and distractions of modern western life.

Elsewhere, in contemporary debates, theories are gaining ground – panpsychism among them – that suggest consciousness may be a fundamental feature of reality rather than simply a property or product of the brain. Critics of this view, including the neuroscientist Anil Seth, point out that it wasn’t all that long ago that people believed a mysterious élan vital must be responsible for the miracle of life. That theory, they say, proved unnecessary. The same will no doubt happen once consciousness and its material basis are better understood.

That seems a distant prospect at the moment. Everywhere, from philosophy of mind through to the ever-growing ‘spiritual-not-religious’ demographic, serious interest is being paid to an intriguing possibility: that contemporary common-sense assumptions about a solely material reality may be more an artefact of how our culture has developed in recent decades than a reflection of the actual state of things.

An important recent work in this vein is The Matter with Things: Our Brains, Our Delusions and the Unmaking of the World (2021), by the psychiatrist Iain McGilchrist. Taking as his starting point the idea of the bilateral brain, whereby the left and right hemispheres contribute to fundamentally different ways of processing reality, McGilchrist wades deep into the worlds of science and metaphysics and provides powerful and credible backing for non-physicalist theories of consciousness.

Readers of influential works in this vein, perhaps especially Kripal’s The Flip (2020), might find themselves experiencing a sort of philosophical vertigo as all manner of possibilities open up, from near-death experiences as moments of genuine revelation to the idea that presences or voices we might usually be inclined to write off as aspects of our own psyches may in fact be sentient beings with independent existences of their own.

Much of this is a far cry from the sober and much-needed research into therapeutic applications of psychedelics being undertaken by scientists such as David Nutt and Robin Carhart-Harris. One need have no particular philosophical commitments in order to benefit, it seems, from the pioneering therapies currently in development. Yet a number of volunteers for these therapies report that their experiences while on psilocybin carry a profound sense of truth and meaning, aside from – though perhaps connected up with – the retreat of their symptoms.

Meanwhile, philosophers including Peter Sjöstedt-Hughes are starting to suggest that some of these experiences might usefully be ‘integrated and evaluated with recourse to metaphysics’ (‘On the Need for Metaphysics in Psychedelic Therapy and Research’, Frontiers in Psychology, March 2023). Psilocybin patients, he argues, might be less likely to reject some of their experiences as ‘delusional’ if they were shown the congruence that they appear to have with worldviews put forward by thinkers such as Plato and Spinoza.

Quite where all this will go, it is too early to say. There are those who fear the weakening of regulations for psychedelics: given their potency, the ‘shroom boom’ may not be as much fun for everyone concerned as it sounds. For an unfortunate few there is no way back from a bad trip, and there is concern about a burgeoning market for guided psychedelic retreats. Even the rolling out of fully-tested psilocybin treatments may yet be thwarted by national governments or medical establishments.

Still, for all that the future of psychedelics is unclear at present, it is striking to see a 20th-century equivalent to the ‘Outsight’ group that never came to pass in Huxley’s day steadily taking shape: scientists, doctors, philosophers, and writers who are taking psychedelics seriously, and who are capable of encouraging wider society to do the same. Perhaps when  another 70 years has passed, the story of our relationship with psychedelics will look very different.