"I get the strangest feeling. Most of it can't be put into words. The whole world suddenly seems more real at first. It's as though everything becomes crystal clear. Then I feel as if I'm here but not here, kind of like being in a dream. It's as if I've lived through this exact moment many times before. I hear what people say, but they don't make sense. I know not to talk during the episode, since I just say foolish things. Sometimes I think I'm talking but later people tell me that I didn't say anything. The whole thing lasts a minute or two."1

What is being described here? A Salvia divinorum trip, perhaps, or a mystical vision? Actually, this description is a typical account of someone who suffers from temporal lobe epilepsy. The disorder has been known to cause aural, olfactory, tactile, and visual hallucinations, intense bouts of anxiety, déjà vu, jamais vu, sensed presences (the perception that some invisible presence is in the room with you), and a general feeling that humans are part of a greater system or transcendent framework.2 These symptoms can also often be found, independently or combined in innumerable ways, in the religious experience. Also known as the spiritual experience, sacred experience, and mystical experience or vision, "religious experience" will be employed here for convenience because it is frequently used as a default umbrella term. However, it is important to remember that I am not referring to commonplace religious moments, but instead to the incredibly profound episodes that have guided prophets, saints, and visionaries, and sometimes provided the foundations for entire belief systems.

Spiritual traditions, including the great religions, rely heavily on a cornucopia of ghosts, demons, angels, spirits, and deities in myriad forms, as well as communications from beyond our worldly existence. Anthropologists seem to find such beings practically everywhere they look, with some counts reaching over 3,500 throughout history.3 Though supernatural beings are thoughtfully cataloged and analyzed in religio-mystical texts, they often at least partially originate from the unforeseen insights of religious experiences. According to anthropologists John Monaghan and Peter Just, many of the most prominent religions appear to have begun through "the vision of a charismatic prophet [who] fires the imaginations of people seeking a more comprehensive answer to their problems than they feel is provided by everyday beliefs."4 Religious experiences tend to become the bedrock of the various iterations of what Aldous Huxley called the Perennial Philosophy: "the thing--the metaphysic that recognizes a divine Reality substantial to the world of things and lives and minds; the psychology that finds in the soul something similar to, or even identical with, divine Reality; the ethic that places man's final end in the knowledge of the immanent and transcendent Ground of all being--the thing is immemorial and universal. Rudiments of the Perennial Philosophy may be found among the traditional lore of primitive peoples in every region of the world, and in its fully developed forms it has a place in every one of the higher religions."5

Spiritual insight is derived from a variety of sources, including the altered mental states of dreams, psychoactive drug use,6 physiologically induced delirium, pathological insanity, prolonged fasting, and sleep deprivation, as well as from more prosaic methods, such as commonplace thought and delusion. However, the religious experience is one of the most durable and recognizable wellsprings. After excluding the other sources just mentioned, a simplified, archetypal religious experience emerges: a spontaneous occurrence--broadly characterized by the psychologist William James, in The Varieties of Religious Experience, as transient, ineffable, noetic, and passive7--throughout which the human is awake, sober, and psychologically and physiologically stable.

It should be noted that, despite this 8precising definition, loyal believers have granted much leeway to historic figures who have claimed to have had purely religious experiences. When one or more criterion is not met, complications in ascertaining the source--metaphysical or otherwise--of an insight inevitably arise. The quintessential example may as well be that of Jesus in the desert, in which any speculation of his visions' supposedly metaphysical source is forever complicated by his prolonged fasting and probable heat-induced delirium.

In The "God" Part of the Brain, Mathew Alper argues that the spiritual instinct is nothing more than an evolutionary mechanism. He speculates that our brains are hardwired (since an early point in the species) to believe in deities and a greater, transcendent purpose in life. As he says, humanity's inclination toward spirituality "constitutes 'nature's white lie', a coping mechanism selected into our species to help alleviate the debilitating anxiety caused by our unique awareness of death."9 The adaptive niche for this could have arisen because, without these beliefs, life can be routinely experienced as empty, confusing, and depressing, with absolute death looming ever closer.10 Atheists and skeptics might scoff at this notion, but they benefit from all the comforts which modern society affords. Without such relatively comprehensive and stable comfort--routine security, entertainment, food supply, medical attention, the conflict-resolution system known as law and government, etc.--the vast majority of humans throughout history managed their nasty, brutish, and short existences as best they could. It seems plausible that those who believed in a higher purpose would find the motivation to live longer and produce more offspring. Meanwhile, those who did not care as much about life because they considered it meaningless would have a somewhat higher chance of dying younger and producing less offspring.

The preceding is a rough sketch of what would undoubtedly become a more intricate, labyrinthine theory. Discussion centers on our species only out of convenience and ignorance. The spiritual instinct has no clearly identified starting point in Homo sapiens, although its evolutionary function is contingent on the higher capacities of consciousness.11 So, as for probable biological introduction, the spiritual instinct can be traced back through our species in only the crudest of ways.

It seems possible that biology hardwires our brains to be "spiritual". If this psychological overlay is adopted into a dogmatic social construct, the word "religious" could be substituted. This kind of theory has been strengthened by research in neurotheology, an emerging, massively unexplored field of science. One of several claims neurotheology (also known as spiritual neuroscience) has attempted to empirically support is that temporal lobe activity in the brain is the main culprit behind religious experiences.12 (The temporal lobe is one of the four broadly delineated regions--frontal, parietal, temporal, and occipital--of the human neocortex. The neocortex is the outermost part of the brain, wrapped around the lower parts, like the giant cap of a mushroom. As the neocortex is divided into hemispheres, left and right, we have two temporal lobes, one on each hemisphere.)13

Michael Persinger, a neurologist at Laurentian University in Sudbury, Ontario, has pioneered research that seeks to link temporal lobe activity with religious experiences. Persinger developed a device, referred to by pop media as the "God helmet", that sends timed magnetic pulses to the brain's temporal lobes. It is used on blindfolded research participants inside a sensory deprivation room (descended from the isolation tanks of consciousness researcher and ketamine psychonaut, John C. Lilly),14 which is heavily soundproofed to create an artificially quiet environment, and surrounded on all sides by a giant Faraday cage to block Earth's magnetic fields. The results reported by participants have often resembled common accounts of religious experiences. "One woman believed her dead mother had materialized beside her. Another felt a presence so powerful and benign that she wept when it faded. British journalist Ian Cotton understood that he was, and always had been, a Tibetan monk."15 Psychologist Susan Blackmore said she felt something "get hold of my leg and pull it, distort it, and drag it up the wall [...] Totally out of the blue, but intensely and vividly, I felt suddenly angry [... Later it] was replaced by an equally sudden fit of fear."16 According to Persinger, while having their brains stimulated by the helmet, four out of every five of his research participants reported the kinds of abnormal experiences that could be interpreted as seeming religious or mystical.17

Persinger's God helmet is related to the method of brain manipulation known as transcranial magnetic stimulation (TMS). TMS has been used in a variety of experimentation and clinical frameworks, perhaps most visibly as an alternative treatment for depression.18 Both the God helmet and TMS use electromagnetic induction to activate weak electric currents in the brain, but there are some major differences. First, the helmet creates magnetic fields that are often six orders of magnitude weaker than those produced by traditional TMS. A common magnetic field generated by the helmet only reaches around one microtesla,19 which is about a thousand times weaker than what's produced by a typical fridge magnet, and about a million times weaker than what's produced by TMS. Second, TMS normally uses simple, predetermined repetition to time its magnetic pulses, whereas the God helmet bases its pulses on real-time measurements of the participant's physiological processes, syncing, for example, to the rhythm of the brain's amygdalae.20

During Persinger's research, it was discovered that there lived an adolescent girl who claimed to be tormented by paranormal events--including one event she interpreted as impregnation by the Holy Spirit--every night while she tried to sleep. Her room was believed to be haunted because when she was in it, she was swept up by inexplicable waves of fear, anxiety, and sensed presences. It had so traumatized her that she barely ever went inside her room anymore, and her family was considering selling the house. They were visited by researchers equipped with devices for measuring, among other things, the magnetic fields surrounding the area. Nothing seemed out of the ordinary at first. Eventually, though, a certain clock radio, which the girl kept close to her bed, was found to be emitting the kind of complex, microtesla-range magnetic pulses that are known to cause seizures in sensitive humans.21 Once the clock radio was removed, the girl stopped reporting paranormal activity and was apparently "cured".22 The case helped bolster the suggestion that there is indeed some connection between magnetic fields affecting the brain and accounts of the paranormal.

Andrew Newberg, a prominent researcher in the field of brain imaging at the University of Pennsylvania, has peered into the brains of research participants as they engage in meditation or prayer. Regardless of participants' preferred spiritual traditions and belief systems, they were all given the same generic instructions and told to enter into a meditative state, or communion with their deity. Newberg's results showed that across all the different prayer or meditation types he tested, the temporal lobes were significantly activated.23 This helps suggest to him that the brain is "hardwired for religion".

The basic theory developed by Michael Persinger and his colleagues purports to explain why some people are more prone to religious experiences than others. Their individual proclivities are directly related to how susceptible their temporal lobes are to external or internal influence. External influences could include everything from large magnetic fields occurring naturally on Earth, to the malfunctioning clock radio mentioned earlier, to list but two examples. Internal influences include, among other things, disorders such as temporal lobe epilepsy. Numerous experiments have suggested that these physical, not metaphysical, influences on the temporal lobes can cause perceptions similar to those reported in religious experiences, and that certain people are greatly susceptible to these influences while others are apparently immune. The implication is that many people who report mystical, other-worldly experiences might have actually been affected by more mundane, worldly phenomena. Some religious experiences could be explained by activity in the temporal lobes or other areas of the brain, with others remaining unexplained. The brain is extremely complex, and we are continually learning more about it, so perhaps in the end it may be shown that a vast amount of religious experiences have rational explanations behind them. Neurotheologists engaged in these efforts generally do not intend to link all religious experiences to rational explanations (and, in any case, they cannot do so, regardless of their intent24).

Saint Teresa of Ávila is one of the well-known historic figures who claimed to have vivid religious experiences, including hallucinations and having the sense that Jesus stood invisibly beside her.25 Her stance was that her experiences were supernatural visions in communion with God. There are two rational explanations that could be offered as alternatives. First, she might have suffered from a mental disorder affecting the temporal lobes. Perhaps it was simply temporal lobe epilepsy. This serious brain disorder could have easily induced perceptions that, for lack of alternative explanations during the sixteenth century, were attributed to supernatural influence. Second, her temporal lobes might have been much more sensitive to magnetic fields than those of the average person, and naturally occurring phenomena in her external environment might have triggered her episodes. Such alternatives are a bit unromantic compared to the traditional explanation. Importantly, though, both alternatives rely on phenomena (a mental disorder and electromagnetism) that have extensive grounding in empirical research. However, Teresa lived during a time when these explanations did not exist (indeed, most of neurology did not exist), and she was of a deeply religious disposition prior to the onset of her visions. It is easy to see how, given her upbringing and circumstances, she would have been strongly inclined to attribute anything extraordinary to her religion.

Alluded to above were other neurological causes of religious experience not reliant on the temporal lobes. Chronic migraine headaches with auras is one such cause, which has been discussed in the medical literature for decades and is no longer controversial. Auras involve "'[v]isual snow' or 'tv static', tinnitus, visual loss, increased afterimages and other varieties of visual perseveration being the most prominent symptoms," along with "many types of illusions and hallucinations of non-visual modalities and a large number of neurological symptoms (e.g. numbness, motor weakness, vertigo, ataxia, speech or language disturbances) and neuropsychological phenomena such as the Alice in Wonderland syndrome."26 Some symptoms "bear a remarkable phenomenal similarity to certain so-called paranormal or psychic experiences such as ghost or fairy visions, reading 'auras', precognition, astral projection and others."27 Teresa of Ávila might have suffered from them. The neurologist and medical writer Oliver Sacks is of the strong opinion that another visionary, Hildegard of Bingen, was tormented by these specific migraines with auras. Hildegard's copious images and visions, possibly a result of auras that overtook her, are sampled and discussed in Sacks' The Man Who Mistook His Wife for a Hat.28

As for Persinger's results, they have yet to be independently replicated by other scientists. A Swedish team attempted to and failed, concluding that suggestibility and personality traits--not external magnetic influence--provide a sufficient explanation for what participants have reported.29 Persinger defended his results, built on over twenty years of research, and detailed how sensitively the experiments must be tweaked in order to succeed.30 The procedures, as described by Persinger in his rebuttal, are in their elusiveness and sensitivity perhaps akin to "digital drugs", another understudied phenomenon, in which repetitive binaural beats are used to tease out altered states of consciousness. (Incidentally, Persinger is researching this arena as well.)31 In any case, a new dialogue is emerging between science and spirituality. The temporal lobes appear implicated in spirituality, but there is no single "God spot" or religion center in the brain.32 Instead, spirituality may emerge from complex, interdependent activity across the brain, with some contribution--however slight or critical--from the temporal lobes. And it is far from clear that magnetic stimulation is the best avenue for scientifically exploring religious experiences; so neurotheology could, and likely will, branch off in new directions.

If the results thus far seem unimpressive, it might be useful to note that science has practically no track record of giving up on these kinds of quests for knowledge. There were over two millennia of inconclusive results between when individuals in India and Greece theorized the atom to when Albert Einstein helped to firmly establish its existence in 1905, with his paper on Brownian motion.33 In that light, a few decades of plodding experimentation between the time when the term "neurotheology" was coined34 until the present day seems quite brief.

Are all religious experiences merely aberrations in brain activity caused by physical phenomena; or is there room for deities and the supernatural? Research supporting the former is nonexistent, while the metaphysical beliefs backing the latter are largely reliant on faith and lack convincing evidence.35 It seems highly likely, practically beyond question, that physical phenomena are causing some of the visions and experiences attributed to supernatural influence. The brain is complicated, partly uncharted, and often misunderstood, so we would be wise to learn more about it before categorically ruling it out and asserting divine intervention. While I strongly urge a modern analysis to consider such empirically based possibilities, I think it is also possible that people are having genuine visions that transcend material reality, perhaps in a small fraction of reported cases. As much as we do not know about the brain, we understand less about fundamental reality. We are still grasping at shadows on the walls of Plato's cave.36 Understandably, most scientists and rationalists will remain skeptical or even cynical toward the metaphysical line of reasoning offered by spirituality. Meanwhile, spiritual believers will continue to argue passionately for the validity of intuition and faith.