'The spiritual mind': the neuroscience of spiritual experience.
Eminent psychotherapist Irvin Yalom once wrote that there are four existential concerns that each individual faces: death, freedom, isolation and meaning. (1) The scientific study of religion and spirituality goes to the heart of all four. Of course, investigating religion and spirituality through neuroscience presents numerous empirical questions, but one of the most compelling must be whether it can explain the relationship between the brain and spiritual experience.
Hay (2) and Spilka, (3) in separate studies, reported that approximately one-quarter to one-third of American and British people respectively have had a religious or spiritual experience. Other more recent research has suggested that less than three percent of people have had an intense mystical experience. (4) It is necessary in the first instance, therefore, to acknowledge that spiritual experience is a broad term that may encompass many different and potentially unrelated brain events. Given the introductory nature and scope of this article, an inclusive definition is preferred. For our purposes, a spiritual experience is one that evokes pleasant feelings of wonder, awe and engagement, accompanied by selflessness, timelessness or unity with the environment. (5) For example, Austin wrote: 'During rare, spontaneous moments, experiences of very special quality and great import emerge from the depths of the human brain ...' (6) Although associated with feelings of spiritual connectivity, this secular definition does not require the invocation of a supernatural agent. It also embraces spiritual experience as a continuum that may range from relatively mild engagement to transcendental bliss. The central indicator of its occurrence is subsequently the reports of experiencers themselves. Thus, spiritual experience is a general psychological state that may or may not invoke a religious or cultural interpretation; our interest rests with the brain correlates of stimulating unusual, pleasant, meaningful and connective experiences that are described as spiritual or religious in nature.
In examining the neuroscientific research associated with spiritual experiences this article is structured into three further sections. Next, the studies examining spiritual experience via neuroimaging techniques are reviewed. The second section focuses on the research gathered from brain wave studies during meditation and other spiritual exercises. Finally, the concluding section attempts to highlight the implications of the neuroscientific research.
NEUROIMAGING THE SPIRITUAL EXPERIENCE
Most scientific literature asserts that spirituality is a product of the peculiar mechanisms of the brain. (7) These interpretations make heavy use of neuroimaging techniques which crudely depict the activity of the brain during specific cognitive (thinking) processes. While most scientists regard spirituality as a consequence of brain activity, a slender group of neuroscientists are supportive of spiritual and religious ideology, or at least do not consider scientific explanations to be inconsistent with the (potential) presence of a genuine spiritual realm, including the existence of one or numerous supernatural agents. (8) For the moment, however, causality will be overlooked; whether a supernatural agent stimulates a spiritual experience or not, there is no question that it manifests through the brain.
This section will consider the evidence yielded from neuroimaging studies. These studies include neuroimaging analyses derived from techniques like positron emission tomography (PET), functional magnetic resonance (fMRI) imaging, and single positron emission computed tomography (SPECT). Each of these techniques provides information on neuronal (brain cell) activity through technological proxies such as the decay of radioactive isotopes injected into a subject, and the magnetic properties of a hydrogen nucleus excited by radio frequency radiation, which can map oxygenated blood flow. The data provided by neuroimaging have been central in revealing features of brain activity during various cognitive functions such as language, consciousness and even degree of religiosity. (9) However, before it is possible to appreciate the findings of neuroimaging studies it is first instructive to review the brain structures under examination.
The cerebral cortex of humans is relatively larger than those of other mammals and consists of four lobes: occipital, parietal, frontal and temporal. The temporal lobe is of particular interest to us because it houses the limbic system, which along with parts of the brain stem is amongst the oldest legacy of evolution. The limbic system is believed to be responsible for generating emotional reactions to the information it receives from the five sensory channels. Roughly, this response is subsequently shunted to the frontal lobes where the higher brain functions of conscious thought and goal-directed activity take over. (10) Both the cruellest and the most exhilarating emotional experiences are an outcome of the primal reaction of the limbic system and the cautious rationality of the forebrain. (11)
The limbic system also contains the hippocampus and amygdala. The former is believed to be involved with recording memories, particularly those with strong emotional content. Pathology in, or damage to the hippocampus, has been associated with changes to spiritual and religious beliefs, as well as changes to long-standing values. (12) The amygdala is believed to play a senior role in coordinating unconscious emotional states. Noteworthy is its connection with the autonomic nervous system. Physiological responses to stressful emotional experiences like 'fight or flight' are largely orchestrated by the amygdala. In addition, because it is linked to the prefrontal cortex, it has a hand in the conscious awareness of emotion. One consequence of these connections is that spiritual experiences are both channelled and interpreted with assistance from the amygdala. For example, Persinger showed that spiritual experiences are, at least partly, an artefact of anomalous but temporary amygdala activity. (13) The limbic system is inescapably pivotal to any brain study of spirituality because of its role in emotion and memory. (14)
Saver and Rabin proposed that pointers toward the neural correlates of religious or spiritual experience can be found in studies of neural pathology (disease) such as those that accompany temporal lobe epilepsy, near-death experiences and drug-induced hallucinations. (15) They argued that the brain dysfunctions associated with these conditions are likely to be responsible for feelings of depersonalisation, timelessness and mysticism. For Saver and Rabin, spiritual and mystical experiences are limbic in nature, dysfunction in the temporal lobe a clear marker.
Similarly, Wuerfel et al. examined neural activity in epilepsy patients who had reported heightened religiosity. (16) They determined that patients with high ratings on a religiosity sub-scale had significantly smaller right hippocampi. It is noteworthy, however, that epilepsy and hallucinations seem to require less activity in the frontal lobe (17) where higher reasoning occurs, whereas Newberg et al. (18) found increased activity in this area during meditation and prayer. This might account for the observation that in pathological circumstances there is limited or no awareness of reality during spiritual experiences, whereas in individuals with healthy hippocampi there are reports of a hyperawareness of reality during spiritual experiences.
Persinger is perhaps the most vehement exponent of the temporal lobe dysfunction explanation of spiritual and religious experience. He claimed in his neurophysiological analysis of spiritual experience that the transient sequences of stimulation to the temporal lobe that accompany temporal lobe epilepsy--specifically within the amygdalohippocampal complex--lead to what he called 'the God experience'. (19) Persinger stipulated that the characteristics and intensity of religious and mystical experiences can be correlated along a continuum against temporal lobe stability; the more unstable, the stronger the experience. Spiritual experiences may be brought about by neuronal (brain cell) electrical instability in the amygdala and hippocampus leading to a brief seizure, vascular anomalies, or cellular membrane dysfunctions. In short, Persinger argued, the structures deep in the temporal lobe are subject to occasional weird activity. A small amount might come about naturally leading to intense thoughts about the nature of the universe, deja vu, depersonalisation, the feeling of being watched or in the presence of someone or something invisible, or a loss of awareness of time. (20) A large amount might come about through pathology such as in temporal lobe epilepsy, and can lead to spiritual revelations, powerful feelings of religiosity or even the conviction of communicating with a deity. (21) One fascinating stream of Persinger's research has led to controversial lab results showing that a sensed presence can be manufactured by passing a weak, pulsating magnetic field over the brain's right hemisphere. (22)
Noteworthy are the populations from which Persinger and others investigating temporal lobe abnormalities have drawn their samples. By definition, temporal lobe pathology studies require clinical populations. This choice has clearly yielded useful results, but a problem lies in the direction of causality. It has been established that pathology in the temporal lobe can lead to heightened religious or mystical experiences, but the preconditions of the same experiences in populations with no temporal pathology have been comparatively overlooked. Can it be hypothesised that all spiritual and religious experience is characterised by temporal lobe abnormality? Do healthy individuals that undergo spiritual experiences simply have a momentary problem in their temporal lobe? For example, Puri et al. showed that there was an increase in left frontal lobe blood flow during religious delusions accompanied by some left anterior temporal lobe flow, a finding largely consistent with epilepsy research. (23)
While the temporal region of the brain is clearly correlated with spiritual experience, the assumption that it is the cause, or an exclusive correlate, does not necessarily sit well with other interpretations that suggest spiritual experience is less of a local and more of a complexly distributed phenomenon. (24) This distributed activity is exactly what Newberg et al. demonstrated in their measurement of cerebral blood flow during meditation. (25) In other studies led by Newberg, brain imaging data showed increased electrical activity and blood flow to the inferior (bottom) frontal and dorsolateral (upper side) prefrontal cortical regions of the brain during meditation and prayer. (26) This means that it may not be so easy to identify Persinger's 'God spot' or Alper's (27) 'God part of the brain'. On the other hand, there does appear to be a patterned process of brain activity associated with reported spiritual experience during neuroimaging studies.
Atran proposed that spiritual and religious rituals like hyperventilation, deep-breathing meditations, walks in attractive environments and chanting cause sensory stimulation and significant activity in the hippocampus, amygdala and hypothalamus. (28) Atran hypothesised that an over-stimulated amygdala becomes hyperactive leading to feelings of emotional intensity. The hypothalamus subsequently receives an overload of raw information that it pushes through the autonomous nervous system, cascading through the sympathetic and parasympathetic branches. The former is responsible for preparing the body for action, while the latter for quietude. This means that the body is simultaneously undergoing heightened heart rate, muscle tone, and hormonal output, as well as the physiological responses encouraging relaxation, tranquillity and calmness.
The collision between the two systems inevitably leads to the sovereignty of one or the other. For example, in meditative states, the parasympathetic system tends to win, with the augmented sympathetic system adding a raised perceptual sensitivity. In this way, an individual remains alert, focused and intense without compromising a relaxed state. In contrast, more frenzied mystical states like those associated with chanting and trance-possession are characterised by sympathetic nervous system dominance. Here, prolonged and heightened arousal is followed by a serene, post-sexlike pleasure.
Attention of the kind associated with meditation is well-accepted as a global prefrontal brain function, but paradoxically researchers have noted that transient decreases in prefrontal activity occur as well. (29) This seemingly contradictory state might account for conscious alertness without much in the way of conscious content; the stereotypical 'nothingness' associated with mystical accounts of meditation. When meditators focus intensely on a single target, its importance amplifies until it becomes the almost exclusive content of working memory. This temporary but complete occupation of memory may disengage most other cognitive capacities of the prefrontal cortex, potentially explaining its periodic lapse in activity. Of course meditative focus may take many forms. A Buddhist meditator might contemplate worldly compassion while a Franciscan nun might concentrate on the love of God. (30) In addition, Newberg et al. found that during spiritual experiences, the flow of information increases to the frontal lobes but diminishes to the posterior superior parietal lobe. (31) The precise mechanisms are uncertain, but given that the frontal and parietal lobes have a role in temporal and spatial orientation respectively this may explain the blurred experience of time, and perceptions of diffused personal boundaries that seem to merge with a fluid universe. Becoming 'one with the universe' may be prosaically explained by a temporary overload or lapse of information to the parts of the brain that manage an individual's sense of self.
In d'Aquili and Newberg's neuroimaging SPECT studies of Buddhist meditators and Franciscan nuns during prayer, for those subjects who reported changes to their normal boundaries of self perception, there was a decreased blood flow to the posterior section of the parietal lobe. (32) Consistent with Atran's view, d'Aquili and Newberg argued that their evidence leads to the speculative proposition that 'unitary', 'cosmic' or 'God' consciousness--where time and space boundaries are ambiguous--occurs when sympathetic and parasympathetic systems fire simultaneously at maximal levels before one is overshadowed. Unfortunately, the specific neural activity as well as the neuro-chemical processes underpinning this nervous system collision remain unclear given the invasive requirements of the type of research needed. Austin, however, reported that the available evidence suggests that meditation on a singular focus leads to an over-stimulated cerebral cortex, which in turn excites the reticular nucleus of the thalamus. (33) The chain of causality leads the reticular nucleus to block sensory impulses so that they can no longer be transmitted. This inhibition shuts down the cortex and releases a complex flood of neuro-chemicals. One study reported increased dopamine activity during meditation related practices. (34)
A pivotal study which examined blood flow in the brain via a PET scan during religious practice focused on a group of six subjects who had experienced a spontaneous religious conversion. (35) Compared to religious practitioners who had never had such an experience, it was determined that the converted group had significantly increased blood flow to the supplementary motor area (linked to the planning of motor acts), the right dorsolateral prefrontal cortex (linked to memory retrieval and monitoring of thought) and the right pre-cuenus (linked to visual working memory). The tentative hypothesis that arises from this combination is that the supplementary motor area was working on religious schema, engaging the right dorsolateral prefrontal cortex and the right pre-cuenus to access a previous, high-impact experience. In other words, a single major experience might be sufficient to permanently change the brain's activity, or even facilitate further experiences. From a physiological viewpoint it is no wonder that for some people a single spiritual experience can transform their lives.
Neuroscientific approaches tend to discard religious and cultural interpretations of spiritual experience. Spiritual experience is a generic term to describe the psychological correlate to brain conditions that probably come about in the first instance from any stimulus that activates the sympathetic and parasympathetic nervous systems simultaneously. Concrete perceptions of time and space rely on a carefully balanced set of brain conditions. Spiritual experience may be no more exciting than a temporary imbalance.
The limitation of neuroscientific accounts of spiritual experience so far is that they focus on neuroimaging data, which are constrained in their ability to observe neural and neuro-chemical activity. (36) In addition, neuroscience has been mostly concerned with either brain activity associated with pathologically-induced hyper-religiosity, or neuroimaged activity during attempts at stimulating a spiritual experience through such techniques as prayer and meditation. Although less sophisticated, studies of brain wave activity during meditation provide a useful supplement.
BRAIN WAVE MEDITATION STUDIES
Brain wave measurement provides an avenue for interpreting cognitive states. Electroencephalograms (EEGs) measure the amount of electrical activity occurring in brain cells or neurons. This brain activity is usually measured in hertz across five frequencies, from the fastest to the slowest: gamma, beta, alpha, theta and delta. (37) Gamma waves appear to be involved in higher mental activity such as perception, problem solving, and consciousness. Beta waves are associated with awake and mentally alert conditions. Alpha waves are common during physical and mental relaxation, or during fantasising, daydreaming and visualisation. Theta waves are characteristic of early stages of sleep and meditative or trance-like states. Delta waves occur during deep but dreamless sleep yet also can occur during certain kinds of altered states of awakened consciousness.
According to Dietrich, there are two common features of meditative states. The first is that sensory input is gradually diminished. (38) The resultant quiescent state is responsible for the range of well-known physiological reactions associated with relaxation. The second is that meditation involves a sustained concentration and awareness through a focus upon a particular target. Dietrich noted that early studies of meditation found alpha wave activity across the frontal lobe. This was somewhat paradoxical as alpha waves are associated with general mental relaxation; it is more logical to expect beta activity in the brain, which is associated with attentional focus and awareness. Furthermore, Dietrich pointed out that if meditation is a genuine path to higher consciousness, then it would engage the brain's highest levels of functioning. However, the detection of alpha waves contrasts with neuroimaging data that has revealed enhanced neural activity in the prefrontal cortex.
A possible explanation might be found in the limitations of the EEG as a technique. EEG measures summed postsynaptic electrical activity of a large section of the cortex at once. This means that beta activity might be concealed by the noise of other overlapping signals including alpha waves. Alternatively, the attention hypothesis, where meditators magnify their focus until it becomes the singular content of working memory, may provide an explanation. Such an occupation of memory may subsequently disengage all other cognitive capacities of the prefrontal cortex, potentially explaining the alpha wave activity. However, there may be one more interesting explanation: meditation engages the highest levels of consciousness and the lowest in a kind of synchrony, and may even leave a lasting impression on the brain.
Studies measuring brain waves during altered states of consciousness tend to observe a change toward slow-wave synchronisation. During these periods, the brain experiences high-voltage, slow-frequency wave activity directed from the limbic system, and where brain stem connections allocate synchronising patterns into the frontal cortex. In Winkelman's words: 'This integrates activities of different levels of the brain with coherent brain wave impulses from lower brain structures through the frontal cortex, producing a synthesis of behavior, emotion, and thought.' (39) For example, Aftanas and Golocheikine used EEG to identify and categorise brain wave states of subjects performing meditation to a reported 'bliss'. (40) During the blissful states, there was an increased synchronisation of brain waves dominated by theta. However, during the precursory states of internal focus there was a discernable synchronisation between alpha and theta waves, suggesting a relationship between internalised attention and blissful experience.
Using two sample groups consisting of eight long-term Buddhist meditators and ten non-meditating students, Lutz et al. investigated the neurological impact of meditation as measured by EEG. (41) By comparing baseline, non-meditative EEGs for each individual, as well as contrasting the EEGs of the two groups, they concluded that the Buddhist practitioners were able to self-induce high amplitude gamma-band oscillations and phase synchrony during meditation, an EEG pattern contrasting those in the student group. Furthermore, the ratio of gamma-band activity (25-42Hz) to slow oscillatory activity (4-13Hz) was higher in the resting baseline before meditation for the Buddhists than the students, rose even higher during meditation, and remained higher than the baseline measure after meditation. Lutz et al. suggested that these data demonstrate that meditation produces both short-term and long-term neural changes. These results were reinforced by a series of studies conducted by Carter et al. (42) and Lehmann et al. (43) which provided evidence that different types of meditation lead to clear short- and long-term changes to neural activity. It also strengthens speculation about a relationship between focused styles of meditation and changes in neural activity in the prefrontal cortex. (44) Attention, it would seem, is pivotal in affecting the mechanics of activity in the prefrontal cortex.
The two strands of research reviewed converge with the following suppositions about brain activity during spiritual experiences. First, there may be the simultaneous firing of both the sympathetic and parasympathetic nervous systems. Second, this leads to activity in the emotional centre of the brain--the limbic system--culminating in a temporarily unusual set of conditions in the hippocampus and amygdala, which subsequently impacts the cerebral cortex where higher reasoning occurs. Finally, the spiritual exercises employed to stimulate experiences encourage brain wave synchronisation, which in itself may represent an unusual set of activities that can precipitate a spiritual experience. The question remaining, however, revolves around the implications of these three empirical observations.
IMPLICATIONS AND UNRESOLVED QUESTIONS
As a cautionary note, it should be acknowledged that religious scholars like Bulkeley have criticised neuroscientific interpretations of spiritual experience. (45) Such criticism has several strands. First is a question mark over the veracity of neuroimaging analyses derived from sophisticated techniques like PET, which charts radioactive tracers in brain blood flow. Bulkeley claimed that the interpretation of neuroimagery is inconsistent and wrought with speculative assumptions given its crude macroscopic perspective. A second major objection is connected to an implicit belief that neuroscientists carry inherently anti-religious tendencies which they import into their analyses. Some neuroscientific interpretations also have a tendency to side-step evidence that disputes a rigid form of localised causation. Also, d'Aquili and Newberg observed that the specific neuropsychological components of an experience may be influenced by the strength of an individual's affectual (emotional) response and their inclination to attribute significance to the experience. (46) As a result, relying on the reports of individuals who have experienced spiritual episodes may be inherently troublesome.
Livingston (47) described the temporal lobe model as a strongly reductionistic, even eliminativist, approach, which of course all neuroscientific interpretations hold common. The power of the current proposed reductions is driven by their unprecedented specificity and the possibility for experimentally-induced mystical experiences of the sort with which Persinger has enjoyed some success. Nevertheless, Livingston identified two reasons why this temporal lobe neuroscientific reductionist approach is not yet the whole story.
First, the changes to the brain described by the temporal lobe model do not in all circumstances come accompanied with a mystical experience. Nor do seizure disorders commonly enough precipitate greater religiosity that they can be attributed as a definitive causal mechanism. Second, although the majority of people have not undergone a mystical experience, the majority of people do actually believe in supernatural agents. Thus, belief does not require a personal transcendent experience; they are neither necessary nor sufficient for belief to come about in the first place or be transmitted in the second. This evidence, according to Livingston, is an obvious refutation of any assumption that spiritual experience is a necessary feature of religion.
It is also worth noting that neuroscience is only one of many avenues for the scientific exploration of spiritual experiences. For example, the application of cognitive science to religion has brought alternative interpretations of the development and propagation of religious concepts. Barrett's assessment concluded that the apparently extraordinary thoughts and behaviours that are associated with religion are underpinned by ordinary, or what he called 'natural', cognition. (48) Thus, in Barrett's view, the cultural phenomenon labelled religion is the product of 'aggregated' but ordinary cognitive processes. An example might be found in the experiments conducted by Birgegard and Granqvist, which supported the theoretical proposition that there is some form of correspondence between the cognitive workings associated with conceptions of parents, and those associated with God. (49) The cognition behind spiritual experiences might not be so abnormal. In fact, as Atran pointed out, we know little about the neuroscience of day-to-day faith. (50)
Descartes developed what is known as the mind/body problem. In essence he sought to answer what separates humans from material objects. His answer proposed the presence of a mind substance and a Divine Substance that exists over and above material objects. He reduced humans to the material body, the mental substance of the mind and the Divine Substance of spirituality. In separating these substances, Descartes avoided having to deal with their interconnectivity including the troublesome issue of causality. Despite side-stepping this problem, Descartes gave rise to one of the most popular ideologies associated with the mind and spirituality, that of dualism, where the mind is a special spiritual substance that overlords the brain, but is separate from it. Neuroscience strikes at the heart of dualism because it demonstrates that the brain and the mind are the same phenomenon.
For those who believe that thought and feeling emanate from the brain, it is difficult to accept the presence of an immaterial soul. After all, if humans are nothing more than the products of material mechanisms (and truth, beauty, love and free-will can be expressed as the interaction of brain chemicals and neurons) then everything that gives meaning to life, including religion and ethics, has no deeper authority. As Simon Conway Morris observed: 'One of the paradoxes of science is that its very greatness as an intellectual adventure is perversely mirrored by a crippling diminution of what it is to be human.' (51)
As a discipline, neuroscience is uniquely equipped to examine the brain activity corresponding to spiritual moments as well as other sublime experiences including those stimulated by music, art, religion and love. However, although powerful, neuroscience is unequipped to explain the meaning and significance of these experiences. In this respect, Conway-Morris' perspective somewhat misses the point. Neuroscientific explanations for spiritual experience do not lead to a diminution of what it means to be human because the quintessential feature of humanity is experience itself. Reducing experience to neuroscience does not affect the impact of spiritual experience. There is always the danger, according to Dennett (52) of 'greedy reductionisms'. This occurs when the phenomenon in question is 'explained away' instead of being explained, with no further understanding of the target. The obvious example concerns the relationship between psychology and neuroscience. If psychological states are reduced to the biochemical interaction of neurons, then a greedy reductionism may be said to have occurred. In other words, reductionism is acceptable, even desirable, until such point as it provides no further explanation of the original phenomena. Of course, there is also much debate about where this point occurs.
Put in simple terms, brain imaging studies tend to show that intense meditation and prayer increases activity in the front part of the brain and decreases activity in the area of the brain that orients our bodies in space, encouraging a blurring of the normal sense of self. (53) This brain activity can stimulate feelings of mystical unity, 'oneness', peace and even the sensed presence of God or other invisible entities. (54) In fact, Newberg, d'Aquili and Rouse argued that there is more than one form of this experience in terms of brain activity, and it does not really matter what stimulus caused it. (55) Studies have even demonstrated that the brain can be 're-wired' as a result of long-term meditation or prayer. (56) Austin, for instance, found that the patterns of neural activation in highly experienced meditators are different from those of the general population. (57) Further studies have revealed that meditators and those who have practised prayer regularly over a long period can experience a form of addiction to the neuro-chemical and other neurological impacts of their activities. (58)
Kozart proposed that a definition of religious experience based on the perceived sensory awareness of God or the divine does not necessarily represent a quintessentially religious experience, given the diverse range of spiritual traditions that do not invoke a supreme being. (59) Moreover, he argued, dysfunctional temporal lobe and limbic activity may be interpreted within culturally constructed religious assumptions, but should not be confused with the original brain stimuli in the first place. In other words, spiritual experience emanates in the brain, but is interpreted by cultural conditioning; spiritual experience may be in the mind, but God is in culture. A relatively strong consensus has emerged from those studies which employed neuroimaging techniques to investigate spiritual experiences. In particular, these studies have reported a central role of the frontal and parietal lobes, as well as the thalamus and limbic system, despite different research protocols and instigative spiritual practices. (60) In addition, the evidence from brain wave studies during meditation has revealed the presence of synchronised activity.
Newberg and d'Aquili posed and answered their own question: 'Can all spirituality and any experience of the reality of God be reduced to a fleeting rush of electrochemical blips and flashes, racing along the neural pathways of the brain? Based upon our current understanding of the manner in which the brain turns neural input into the perceptions of human experience, the simplest answer is yes.' (61)
Is mysticism in the mind? The problem has been described in terms of mutually exclusive possibilities where either spiritual experience is just a neurological construct created by and executed within the brain, or the blissful, unitary and selfless states described by the mystics do exist and the mind can perceive them in extraordinary circumstances. (62) Newberg and d'Aquili conceded that brain science can neither prove nor disprove the existence of mystical notions with simple answers. (63) On the other hand, neuroscience does show that the spiritual experiences described by mystics are legitimate, lending support to the importance of their psychological salience and impact.
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AARON SMITH / HISTORY AND PHILOSOPHY OF SCIENCE