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The Psychedelics and Religion
by Walter Houston Clark
from: Psychedelics, edited by B. Aaronson and H. Osmond
This document in other languages: Hungarian -


In 1968 Ralph Metzner wrote of Walter Houston Clark, (in The Ecstatic Adventure)

THERE ARE NOT too many men in their sixties, professional academics at that, who have preserved sufficient openness to experience and receptivity to new ideas to accept the idea of personal experimentation with psychedelic drugs. Old age is too often synonymous with rigidity rather than wisdom. Not so with Walter Houston Clark, Professor of Psychology of Religion at Andover Newton Theological School in Newton, Massachusetts, former dean and professor at the Hartford School of Religious Education, author of The Oxford Group (1951) and The Psychology of Religion (1958), and founder of the Society for the Scientific Study of Religion.

In an article on "Mysticism as a Basic Concept in Defining the Religious Self," Professor Clark wrote that

The [psychedelic] drugs are simply an auxiliary which, used carefully within a religious structure, may assist in mediating an experience which, aside from the presence of the drug, cannot be distinguished psychologically from mysticism. Studies have indicated that, when the experience is interpreted transcendentally or religiously, chances are improved for the rehabilitation of hopeless alcoholics and hardened criminals. Even though observations like these mean that the psychologist can learn a little more of the religious life, in no sense does it ultimately become any less of a mystery. Though man may sow and till, winds may blow and the rains fall, nevertheless it is still God that gives the increase.

Today, amid the confusion of grave problems caused not so much by decades of "drug abuse" as by decades of increasingly futile attempts to legislate away the use of prohibited substances by pious decree, it is all too easily forgotten that the rediscovery of the psychedelic drugs mid-way through the present century was as promising a find as mankind has seen. A significant, if minority group of our best scientists, doctors, philosophers, writers, artists, and intellectuals of every description began explorations with the psychedelics, a search that was really only the continuation of an age-old quest involving the great majority of peoples and tribes of the ancient world. Psychedelic drugs have, in fact, been used as religious and curing aids since the very beginning of human existence, and only in the 1950's was any significant "scientific" research begun using them.

This research planted the seeds of a revolution of a kind that science purportedly thrives upon, but the sprouting of the seeds was aborted early on by scandal. In the following article we read about some research that was later to be ignored not so much because it was scandalous, but because it challenged some of the underlying paradigms of the entire scientific enterprise. Some of the findings of psychedelic research seemed to herald a merging of the "scientific" and "religious" or "mystical" viewpoints, despite very powerful resistance by both sides to opposing views. The scientific viewpoint had for a long time generally disdained religion as primitive superstition, and religious thinkers of every denomination had tended to view the destructive uses to which science had been put as evidence of its ultimate inability to advance the human condition. Yet some scholars such as Professor Clark saw the rediscovery of psychedelics as the key to the blossoming of a new view. In the words of Alan Watts,

For a long time we have been accustomed to the compartmentalization of religion and science as if they were two quite different and basically unrelated ways of seeing the world. I do not believe that this state of doublethink can last. It must eventually be replaced by a view of the world which is neither religious nor scientific but simply our view of the world. More exactly, it must become a view of the world in which the reports of science and religion are as concordant as those of the eyes and the ears. (Preface to The Joyous Cosmology, 1962).

In retrospect, it will be seen by historians of the 21st century that the scandal of the 1960's was not Dr. Timothy Leary leading a generation down the road to a drugged oblivion, (for that generation is today doing quite well!) but rather that such Puritanical views of mere over-enthusiasm for a new discovery led a generation of scientists and world leaders to throw away what in any other epoch would have been a Holy Grail, a discovery of such fundamental importance that the great discoveries that had made modern technological civilization possible would seem almost trivial by comparison. The situation continues today unabated, despite the continued availability of the wisdom of Professor Clark and the many other pioneers of psychedelic discovery.

Peter Webster

The Psychedelics and Religion


The recent discovery of the religious properties of Lysergic Acid Diethylamide-25 is not such a wholly new phenomenon as some people seem to believe. There is some evidence to suggest that the secret potion that was part of the ordeal of initiation into the Eleusinian mysteries in ancient Greece contained a psychedelic drug. The somewhat mysterious drug called soma, used in India, sometimes for religious purposes, was psychedelic, while the Mexican mushroom whose active principle is psilocybin has been used by the Aztecs for centuries in their sacraments. Their word for it, significantly, meant "God's flesh."

The peyote button, the top of a certain spineless cactus plant, has been and is now used by some members of nearly all the American Indian tribes in cultic ceremonies. The peyote religion goes back nearly a century in historical records and certainly is even more ancient. At present it is represented by the Native American Church, a loose collection of some two hundred thousand members, according to its claim. Peyote among the Indians has had a history of controversy not unlike LSD among whites. However, despite years of repressive laws and legal harassment, there has been little or no hard evidence of claims made as to its harmfulness, and some indication that it has done good. More importantly, laws made to repress its use have been declared unconstitutional in several states on the ground that they have violated constitutional guarantees of freedom of religion.(1)

Perhaps the most distinguished and eloquent advocate of the view that certain chemicals may promote religious states of mind was William James, who some seventy years ago inhaled the psychedelic of his day, nitrous oxide. He referred to this self-experiment, in The Varieties of Religious Experience, in his chapter on mysticism, where he wrote the often quoted words:

. . . our normal waking consciousness, rational consciousness as we call it, is but one special type of consciousness, whilst all about it parted by the filmiest of screens, there lie potential forms of consciousness entirely different.... No account of the universe in its totality can be final which leaves these other forms of consciousness quite disregarded.(2)

But "religion" is an elusive term, and whether or not we can regard states associated with the psychedelics as religious depends on how we define it. Doubtless there are those who would regard any state initiated by the ingestion of a chemical as by definition non-religious. For such people, the reading of this chapter will be an idle exercise. Tillich defines religion as "ultimate concern," while both William James and W. R. Inge speak of the roots of religion as ultimately mystical. Rudolf Otto, in The Idea of the Holy (1958), speaks of the non-rational elements of the religious life in terms of horror, dread, amazement, and fascination as the mysterium tremendum, "the mystery that makes one tremble." Certainly, as I will point out in more detail later, the subject who has consumed the forbidden fruit of the psychedelics will often testify that he has been opened to his own "ultimate concern" in life and may even speak in terms reminiscent of the medieval mystics. Furthermore, one of the chief objections of the opponents of the psychedelics is that for many the experience may be "dread-full," as cogent an illustration of Otto's thesis as one could well expect to find.

Long before I took very seriously the claims that eaters of psychedelic chemicals made as to their religious experiences, I defined religion as "the inner experience of an individual when he senses a Beyond, especially as evidenced by the effect of this experience on his behavior when he actively attempts to harmonize his behavior with the Beyond."(3) Consequently, it would be to this standard that I would refer experiences triggered by the psychedelic drugs, in order to determine whether they should be called religious or not.

From the definition, it will be clear that the core of religious experience is subjective therefore never to be fully shared with another person. Consequently we are forced to rely to a large degree on the words of the religious person for any determination of religion. This necessity disturbs the modern psychologist whose too-narrow conception of his discipline as a science bars him from probing the nature of the religious consciousness despite its cogency as a source of profound personality change. As he observes the conventional churchgoer and hears him glibly using such terms as "conviction of sin "rebirth" "redemption" and "salvation," the psychologist may too hastily conclude that such terms are mere pious language that brings a certain sentimental comfort to the worshiper but hardly represents any marked change in his relations with his fellow men. The psychologist has forgotten, if he ever knew, that such terms are the echoes of experiences that, perhaps many years ago but also today, have transformed the lives of prince and beggars enabling them to unify their lives and attain heights that could have been possible in no other way. It is this effectiveness, along with the subjective reports by subjects of encounters filled with mystery and awe, for which we must be on the lookout as we try to appraise the religious significance and value of these strange chemicals.

But before we start our survey I must say something about the place of the non-rational in the religious life. Notice that I call it non-rational, not irrational. The religious life involves at least three basic factors: First is the life of speculation and thought, the expression of the rational function of the human mind. The second is the active expression of religious principles, the concern for others and the observance of ethics and other social demands that grow out of one's religious commitment. Religion shares these two functions with other interests and duties of humankind. But the third function is unique, and without it no other function or activity can be called religious in any but a very pale and secondary sense. This third function is the experience of the sacred, the encounter with the holy, which not so much logically, but intuitively, or non-rationally, the subject recognizes as that which links him with the seers and the saints of today and of yesterday. A non-drug example will be found in Arthur Koestler's autobiographical The Invisible Writing (1955), in the chapter entitled "The Hours by the Window." It is this non-rational perception of the holy that so moves the individual and interpenetrates both his thinking and his activity, infusing them with tremendous energy and giving to his whole life that stamp we call religious. We must ask whether in any sense the psychedelic substances arouse this factor, to determine whether we can characterize the result as religion.

If we can accept the direction of the argument thus far, that the essential core of religion may be found in the mystical consciousness and the direct experience of the holy, I can show considerable evidence that it is this aspect of the nonrational consciousness that the psychedelic drugs release. I consider my first example sufficiently persuasive to make the point.

Dr. Walter N. Pahnke of Spring Grove Hospital, Baltimore, in a doctorate study at Harvard, used twenty theological students in a double-blind study of the effects of psilocybin. All twenty were given similar preparations; half were given the drug and half placebos; then all attended the same two-and-one-half-hour Good Friday service. The experimental group reported overwhelming evidence of mystical experiences, while the control group reported next to none.(4) The reports included intuitions and encounters with ultimate reality, the holy, and God; in other words the "Beyond" of my definition. Furthermore, a six-month follow-up showed much evidence that the subjects felt they had experienced an enlivening of their religious lives, resulting in an increased involvement with the problems of living and the service of others.

The previous sentence supports that aspect of my definition that emphasizes the active functions of religion, the effect of the experience of the Beyond on the individual when he "actively attempts to harmonize his life with the Beyond." Western prejudices in religion favor the pragmatic test, so claims of encounter with God or ultimate reality are always more impressive when they can be supported by concrete evidence of benefit like this. Further cogent evidence is supplied us in studies of alcoholics treated with LSD by Osmond and Hoffer in the early 1950S in Saskatchewan. According to Dr. Hoffer's report, of sixty difficult cases, half were no longer drinking five years later, while there was a very high correspondence between success and the report of the subject that his experience had been transcendental in William James's sense of the term.(5)

Still more evidence pointing in the same general direction comes from work done by Dr. Timothy Leary when he was at Harvard. He received permission from the State Commission of Correction to give psilocybin to thirty-five inmates at Concord State Reformatory. Since Dr. Leary had reported that the convicts were having religious experiences and the work was controversial, I persuaded him to introduce me to some of them so that I could investigate at first hand. While unable to follow up all the subjects, I talked with those who were still in prison---by and large those who had committed the more serious crimes and so were serving long terms. I found that it was indeed true that these men referred to their experiences as religious in varying ways. One reported a vision in which he had participated with Christ in His Crucifixion. Shortly after this, he had looked out the window. "Suddenly all my life came before my eyes," said this man, an armed robber of nearly forty who had spent most of his adult life behind bars, "and I said to myself, What a wasted Since that time these men have formed, within the walls, an AA-type organization called the Self-Development Group, to rehabilitate themselves and others. I could not deny that there were profound religious forces at work among these men as the result of the drug treatment (Leary and Clark, 1963).

In their book The Varieties of Psychedelic Experience Masters and Houston present a wealth of cases illustrating psychedelic experiences of various kinds. Though nearly all their 206 subjects reported religious imagery of some kind, only a few demonstrated mystical experience of what the authors consider a transforming and integrating kind at the deepest level; but they believe that the drugs do facilitate the latter, making their belief clear chiefly through a remarkable illustrative case in their final chapter. The subject, a successful psychologist in his late thirties, had been irresistibly attracted to what society regards as "evil" from his earliest youth. He believed in nothing, was a militant atheist, was sexually promiscuous, and to his students "preached a gospel of total debauchery." The appearance of neurotic symptoms had led him into a process of self-analysis and therapy, which had been only partly successful. But only three sessions with LSD led this person, through an intricate series of shattering symbolic experiences, to an almost total transformation of self. A year afterward, this transformation was seen by the subject as an encounter with God that had been both religious and lasting. This fact was attested to by those who knew him.

The foregoing is just a sampling of many studies that report religious elements following the ingestion of psychedelic drugs. When the environment suggests religion, a higher proportion, up to 85-90 per cent, of the experiences are perceived as religious by the subjects. Those who resist the religious interpretation are much less likely to experience it, but even some of these, much to their surprise, may "experience God."

The following case is an illustration: As part of an experiment at a mental hospital, I had occasion to guide a young college graduate I will call Duncan Cohen. Brought up as a Jew, he had become a strong atheist and married outside his faith. The investigation required a number of sessions, and the study of its religious aspects was only an incidental aspect of the experiment. The setting aimed to be supportive, the surroundings softened with flowers and music, and the subjects were encouraged to bring with them into their private hospital rooms anything of significance to them, including their choice of music if desired. Duncan was given sixteen daily doses of 180 micrograms of LSD. He was initially irritated by me as a person who taught in a theological school; and, though he came to trust me more and more as the sessions continued, he steadfastly resisted any religious interpretation of the sessions, which, even from the first, he regarded primarily as experiences of rebirth. The early sessions involved a climactic series of symbolic encounters with various members of his family, followed by a dramatic enactment of his own death, in which he acted both as "corpse" and "funeral director," while I was asked to pray as the "officiating rabbi." Still the essentially religious nature of much of these proceedings was either denied or only dimly sensed. I tried to avoid pressing any religious interpretation on him, though my interests doubtless acted suggestively on him.

The climax came after the fifteenth ingestion. About four hours after taking the drug on that day, he had been sitting on the lawn outside the hospital watching two grasshoppers maneuvering in what he interpreted as a kind of cosmic dance. Suddenly, he felt at one with them and with the cosmos besides. I was aware of it only after he caught sight of me and came running over to me in great excitement calling, "Dr. Clark, I have had a mystical experience; I have met God!"

A nine-month follow-up indicated that Duncan regards the total experience as a most significant one. He has continued to grow and mature, as he sees it. There have been some difficult times. "What I regarded as the end of the experience when I left the hospital," he told me, "was simply the beginning of an experience of maturing which is still continuing." He reports more tolerance and open-mindedness, and he recoils when he thinks of what he now regards as his former narrow-mindedness. He has reflected with increased insight on the role of religion in history, history being a favorite subject. I do not know that he is any more hospitable to institutionalized religion, though now he is willing to accept a view of life that for him is more, rather than less, religious than that of the conventional churchgoer. At any rate, psychedelic religious cults, like the League for Spiritual Discovery, have an appeal for him that they did not have before. Religion in a profound sense, in human nature and in history, has more meaning to him.

In the middle 1950s Aldous Huxley published his influential The Doors of Perception, describing an experience with mescaline and advocating it as a means of vitalizing the religious life, with particular emphasis on its mystical aspects. R. C. Zaehner, in his Mysticism: Sacred and Profane (1957), takes issue with Huxley and points out that while mescaline may be able to release pantheistic or monistic types of religion, including those closely associated with psychosis, it cannot be said to stimulate a theistic religious experience. He does not see its use justified by Christian doctrine. Zaehner's reasoning is based partly on a self-experiment with mescaline, and so he cannot be classified with those many critics of the psychedelics anxious to make people's flesh creep without having any firsthand knowledge of what they are talking about. But, commendable though Professor Zaehner's effort may have been, he falls into a familiar fallacy common to all users and non-users of the psychedelics, including Huxley, namely, that of generalizing too widely on the basis of his own personal experience and point of view.

It is true that the religious experience of many of the drug users seems to them to fit more readily into pantheistic and Eastern religious patterns. But the experience itself is essentially non-rational and indescribable. In order that it may be described, one is forced to use concepts of one type or another, none of which seem to do justice to the experience. Consequently these are of great variety, and while some will agree with the Zaehner theological typology, others have no more trouble seeing their experiences as essentially Christian than did St. Teresa when she described one of her mystical visions as revealing to her the secrets of the Trinity. I have known those whose psychedelic experiences have returned them from atheism to the Christian tradition in which they had been brought up, and I have also known those who preferred Eastern concepts.

W. T. Stace, in Mysticisrn and Philosophy (1960), distinguishes between the mystical experience itself, which he finds to be universal in its characteristics, and the interpretation of that experience, which differs from faith to faith and from century to century. Thus the Christian will refer his experience to Father, Son, and Holy Spirit, while the Buddhist will explain an identical psychological experience in terms of Nirvana. Stace further aids us in clarifying the nature of a psychedelic experience in his "principle of causal indifference." This states that what makes an experience mystical is not what touches it off, whether drug or Christian sacrament, but its experiential characteristics. It may then be conceptualized in any way deemed suitable by the experiencer. I may add that, just as a Christian sacrament may or may not stimulate a mystical experience in any given worshiper, the same thing may be said of mescaline or LSD. Stace gives us an example of mystical experience meeting his specifications triggered by mescaline.(6)

In another part of his book, he discusses the experience of pantheism, which so often has gotten the mystic into trouble. Calling the experience "transsubjective," he points out its paradoxical character, in which the mystic may feel himself both merged with the Godhead and infinitely the creature of God at the same time. Consequently, we can understand how, in some sense, mysticism can be felt to be compatible with theism by one mystic and with atheistic Buddhism by another. The same argument will help to explain the variety of theological and philosophical concepts used to interpret the psychedelic experience.

There would be no greater mistake than to suppose, since the psychedelics are frequently accompanied by religious experience, that God, when He created these chemicals, baptized them and segregated them for religious purposes. Indeed, had this been His purpose, it would seem that He has not kept up with His theological and medical reading, for He might have foreseen the difficulties He was preparing for their users. As I have already pointed out, there is no guarantee that a given person will have what satisfies him as a religious experience. However, certain conditions will favor this religious result, and I will indicate briefly a few of the most important.

First of all, there is the subject himself---his nature, and the desire he may have for the religious experience. A person already religiously sensitive is more apt to have a religious experience than one who is not, and one who deliberately prepares himself is more apt to be rewarded than one who is indifferent or unaware of the possibility. Vide the case of Duncan Cohen, who had ingested LSD fourteen times without a religious outcome; the only experimental subject in the Good Friday experiment who failed to report a mystical experience was one who did not believe it possible and deliberately set out to demonstrate this belief, partly by omitting the religious preparation engaged in by the other subjects.

The setting is another factor that favors or discourages religion. If the drug is taken in a church or the subject is surrounded by religious symbolism, he is more apt to obtain a religious result. Appropriate readings at strategic points during the period when the drug is active, say from the Bible or the Tibetan Book of the Dead, particularly when accompanied by religious music, are other favoring circumstances. If the guide is a deeply religious person and anxious to promote a religious outcome, this will be another plus factor. Subjects have reported feeling this with respect to Dr. Leary, and doubtless this helps to explain the high incidence of religious experiences reported in his experiments. It is obvious that all these factors depend for their influence on the suggestibility of the subject. However, it would be a mistake to think that suggestibility will explain it all, since, once the experience gets started, the unconscious of the individual subject seems to take over the direction of matters in large measure. But the initial suggestibility of the subject and the manner in which it is exploited, by himself or by others, will enhance the suggestibility that most investigators feel to be one of the salient characteristics of the psychedelic state.

Critics, to prove their point that psychedelic experiences are not truly religious, often cite the fact that beneficial results do not always last. But in this respect they are no different from other types of religious experience. Every evangelist is well acquainted with backsliders. If personality-changes brought about through psychedelic experience are to be made permanent, they must be followed up.

The issues that the psychedelics pose seem to most people to be in the realm of therapy, health, and the law. They may be more importantly religious. One of the functions of religion---perhaps its chief function---is that of supplying life with meaning. The most luminous source of this meaning, through the ages, has been the religious experience of religiously gifted leaders, the dreamers of dreams and the seers of visions, prophets, converts, evangelists, seers, martyrs, and mystics. According to their enlightenment, these men and women have stood before the Lord, some in joy, some in vision, some in transport, and some in fear and trembling. But however rapt, these are the people who have made their mark on that profoundest function of man's strange sojourn on this earth. Astonished, amazed, offended, and even horror-stricken, the present generation of responsible defenders of the status quo have seen many of those who have ingested these drugs present pictures of such conditions as capture the imagination of youth with a cogency that churches find hard to match. The psychedelic movement is a religious movement. The narrowly restrictive laws that have been passed have made it a lawless movement with respect to the use of the drugs, though generally it is not in other respects.

It has had its parallels in other ages, and it will be instructive for us to take a brief look at history. The early Christians were looked on with some alarm by that magnificent peace-keeping agency, the Roman Empire. Because they refused even that insignificant homage to the divine Emperor that would have satisfied the State, these dissenters were persecuted and led to death in the arena, their persecutors being among the more conscientious of their rulers. Heretics and Jews during the Middle Ages were burned at the stake for engaging in secret rites and the holding of views disapproved by the Church. Among the former were many mystics who had undergone experiences very similar to, and probably often identical with, those of many of the psychedelic hipsters of our times. Sitting in judgment on these sensitive religious spirits (such as Meister Eckhart) were not irresponsible sadists but sober clerics whose business it was to protect other souls from heresy. These judges had no firsthand knowledge of the mystic's vision. They were rational and conscientious men charged with the duty of saving their fellows from the flames of Hell, even as conscientious judges of our time enforce the modern equivalent of the stake as they sentence to long prison terms those whose visions and ecstasy they have never shared. They only know that laws have been broken, and they wish to protect society. They act according to their lights.

But religious people have never been notable for setting law above the dictates of their consciences, and it is this stubborn habit of the human mind that has brought us such protection as religious conviction has against the state. It will also make laws against the psychedelic drugs almost unenforceable. Yet it has been religious conviction hardened into legalism, whether theological or civil, that has led to intolerable controversy, self-righteous cruelties, and some of the most savage wars of history. This shameful record has led to the principle of religious freedom such as that written into the American constitution, which, nevertheless, only partially protects religious minorities from the tyranny of the majority. In general there is no type of religious experience for which the average American, high or low, has so little tolerance as that type fostered by the psychedelic drugs. The reason is that the mystical side of human nature has been so repressed that it is little understood. It has been looked on as esoteric and Eastern, therefore vaguely opposed to the American way of life. Society must be protected against it, say conservative churchgoers, Daughters of the American Revolution, respected members of the academic community, and the American Medical Association.

In order to call attention to a neglected aspect of the controversy over the psychedelics, I have a little overstated a case in order to make my point clear. For certainly I recognize the fact that the drugs have their dangers and need to be controlled, though I wish that legislators and enforcement agencies would make greatly needed research much easier. Some of the world's most experienced and eminent investigators in this area find the drug denied to them. But it is not surprising that cults that see in the psychedelics a sacramental substance of great potency have been growing apace during the past few years, from the Neo-American Church, whose leaders militantly stand on their constitutional right to use the substances sacramentally, to the Church of the Awakening, which is more conservative but which nevertheless has applied to the FDA for the right to use peyote as does the Native American Church. This right, like other religious rights, has been hard won by the Indians through loyalty of cult members, self-sacrifice, and the willingness of individuals to go to jail if need be in support of their convictions. If the Indians can use peyote, it is hard to see why white churches cannot make good their right to do likewise. In the meantime, both legal and illegal use of the psychedelics goes on, sometimes religious and sometimes nonreligious, sometimes with irresponsible foolhardiness and sometimes with the highest resolution that such promising tools shall not be lost to society, at least until their most cunning secrets be wrested from them through careful research and responsible practice.

But there is no doubt that the drugs and their religious use constitute a challenge to the established churches. Here is a means to religious experience that not only makes possible a more vital religious experience than the churches can ordinarily demonstrate, but the regeneration of souls and the transformation of personality are made possible to an extent that seems to be far more reliable and frequent than what the ordinary churches can promise. LSD is a tool through which religious experience may, so to speak, be brought into the laboratory that it may more practically become a matter for study. It is important that religious institutions face the issues raised so that any decisions they may have to make will derive from sound knowledge rather than prejudice, ignorance, and fear. I do not have the wisdom nor does anyone yet have the knowledge to say in advance what the action of the churches will be or ought to be. But I do say that if such decisions are to be sound, they must be based on thorough information, freedom from hysteria, and above all, open-mindedness to what may reliably be learned both of the great promise and the dangers of these fascinating substances.

(1) See Aberle (1966) and Slotkin (1956) for full anthropological accounts.

(2) P. 298.

(3) See my The Psychology of Religion (1958), Chapter 2, for a discussion.

(4) For a fuller report, see the Pahnke article in this volume, "Drugs and Mysticism", Psychedelics, Aaronson & Osmond; also Pahnke, "Drugs and Mysticism' (1966)

(5) See remarks by Abram Hoffer in H. A. Abramson (ed.), The Use of LSD in Psychotherapy (1960), pp. 18-19, 114-15.

  1. P. 71 ff.. See p. 29 ff. for his "principle of causal indifference."