In a passage that has deservedly become famous, the great American pioneer of psychology William James wrote that our normal waking consciousness is just one among the many modifications of which human consciousness is capable. Separated from it by no more than "the filmiest of screens," he wrote, "there lie potential forms of consciousness entirely different. We may go through life without suspecting their existence; but apply the requisite stimulus, and at a touch they are there in all their completeness ..." Ever since I first came across these words in James' classic Varieties of Religious Experiences (1901), I have been aware of their far-reaching implications for practically all dimensions of human culture and most certainly for my own field of specialisation, the study of Western esotericism. In most if not all traditions of rejected knowledge that we study under that label, we find explicit references to other realities, other worlds, or other dimensions than those that we know from our normal waking consciousness. Think of the realm of eternal forms or ideas in the Platonic tradition and the altered states of manía (divine frenzy, or "madness") through which Plato writes we can gain access to them; think of the luminous realms of the Ogdoad and the Ennead described in a famous Hermetic treatise; think of the mysterious "interior heart of creation" that the Christian Theosopher Jacob Böhme claimed to experience in a state of visionary ecstasy; think of the domains of "heaven and hell" that appeared to the Enlightenment visionary Immanuel Swedenborg in an altered state; think of the "nightside of nature," the mysterious spiritual world accessed by somnambulists in the traditions of Mesmerism; think of the "higher worlds" that modern Theosophy and Anthroposophy believe can be accessed through techniques for training one's "clairvoyant" abilities; or think of the spectacular vistas and phenomena described by psychedelic visionaries such as Terence McKenna or Alex Grey. If we wish to understand what practitioners from antiquity to the present really meant by gnosis and equivalent terms for "higher knowledge," it seems evident that we must study the phenomenology of consciousness and the various means and techniques by which it can be modified.
Consciousness may well be the ultimate mystery that lies at the bottom of all other mysteries, even those that may seem the most mundane. While evolutionist-materialist philosophers such as Daniel Dennett dismiss consciousness as an ultimately illusionary epiphenomenon - technically a side-effect of strictly material processes - I find myself convinced by the most influential modern philosopher of consciousness David Chalmers, who points out that consciousness is centrally concerned not with quantifiable processes but with qualia. Being conscious means not just being able to respond to stimuli: rather, it means our truly weird human ability of knowing what it's like to have experiences - for instance, a robot may learn to recognise the movements of a conductor and play Beethoven on the piano, but I am sure that he will never know what it's like to enjoy the music. This ability of ours is what Chalmers calls "the hard problem" of consciousness, as opposed to those comparatively easy (well, easy...) problems for which we may ultimately find technical solutions.
The concept of "altered states of consciousness" (ASCs) was coined by Charles Tart at the end of the 1960s, but because it's not evident that normal waking consciousness itself is a stable baseline state, today most scholars prefer the more flexible concept of Alterations of Consciousness. This new field of research in cognitive studies and related disciplines was kick-started by the psychedelic revolution of the 1960s, for rather obvious reasons: those who might doubt the truth of William James' observations were likely to change their mind after experiencing the spectacular effects of classic psychedelic agents such as LSD, DMT, mescalin, or psilocybin. The legal prohibition of such substances since around 1970 put an abrupt end to scientific research in this domain, although not to clandestine experimentation with psychedelics, which may have been a serious background dimension to many "spiritual revelations" in New Age and other forms of contemporary esotericism. Roughly since the 1990s and decisively since about a decade or so, we are now experiencing a psychedelic renaissance, as the remarkable therapeutic potential of these agents is becoming ever more evident in such domains as psychology and psychiatry.
In a programmatic article published in 2012, I argued that "entheogenic religion" can be defined in a narrower and in a wider sense. It always has to do with the subjective experience of being "filled," "possessed," or "inspired" by some kind of divine entity, presence or force; and while such experiences can be induced by psychoactive substances (entheogenic religion in a narrow sense) they can be induced by other techniques as well, for instance breathing techniques, rhythmic drumming, ritual prayer and incantations, or meditation (entheogenic religion in a broad sense). Accordingly, forms of entheogenic religion that fall within the domain of Western esotericism can be defined as entheogenic esotericism sensu stricto or sensu lato. It is time to get over our culturally mediated stereotypes and prejudices about these dimension of human experience and take them seriously.