Definitions of mysticism and descriptions of mystical experience range widely through literature. The word itself ‘has its origin in the Greek mysteries’ and ‘mystery (mysterium) comes from the Greek verb muo, to shut or close the lips or eyes’. In this original sense, a mystic was a person who had been ‘initiated into the esoteric knowledge of Divine things, and upon whom was laid the necessity of keeping silence concerning his secret knowledge’. But the priests of the ancient mystery religions lost control of the term when philosophers began to use it to describe aspects of their own speculations. From the Greek philosophers it was passed on to ‘the Christian Church, which held itself to be a body of initiates into a truth not possessed by mankind at large’.
Modern uses for terms such as ‘mystic’, ‘mystical’ and ‘mysticism’ range far beyond the ancient applications to pagan and Christian ritual. Most of the contemporary major religions of both east and west have recognised practices that can be understood in these terms. There are also contemporary anthropological observations of traditional tribal practices such as shamanism to which the terms can be applied.
Mysticism in the modern sense refers to a psychological experience involving a conscious transcendence of the normal self identity. The mystic usually believes that he or she has entered into a higher state of consciousness, has made contact with a deity, or has entered into some form of communion with the object of devotion of the religious or philosophical tradition concerned.
There is a tendency amongst some religiously inclined academic analysts to divide mystical experience into different types, according to the category of religious/philosophical tradition to which the mystic is allied. In this way it is sometimes argued that monistic, theistic and nature mysticism, for instance, have qualitative differences.
One leading theorist has divided mysticism into two broad types, extroversive and introversive: ‘The extroversive way looks outward and through the physical senses into the external world and finds the One there. The introversive way turns inward, introspectively, and finds the One at the bottom of the self, at the bottom of the human personality.’ The language of mysticism is often difficult, ‘ineffability’ being one of its characteristics, and ‘the One’ is usually interchangeable with ‘the Absolute’, ‘God’, ‘nirvana’ or some other transcendental objective.
The general consensus seems to be that psychological phenomena that follow certain broad principles can be described as mystical experience. All mystical experience has validity, regardless of the particular path by which it was approached. One exception is that the mystical validity of drug-induced experience is sometimes disputed.
There is hardly any soil, be it ever so barren, where Mysticism will not strike root; hardly any creed, however formal, round which it will not twine itself. It is, indeed, the eternal cry of the human soul for rest; the insatiable longing of a being wherein infinite ideals are fettered and cramped by a miserable actuality; and so long as man is less than an angel and more than a beast, this cry will not for a moment fail to make itself heard. Wonderfully uniform, too, whether it come from the Brahman sage, the Persian poet, or the Christian quietist, it is in essence an enunciation more or less clear, more or less eloquent, of the aspiration of the soul to cease altogether from self and to be at one with God.
Essentially, a mystical experience involves an altered state of consciousness. A metaphor which repeatedly appears is of a house or structure with many rooms in which human consciousness abides. Normally these rooms have to be explored in the dark, but when a person consciously enters a certain room, usually in the highest part of the house, a bright light is switched on which variously blinds, confuses or inspires a person with the inner scene that is revealed.
Plato’s simile of the cave is one of the clearest descriptions of this idea. In The Republic he has Socrates describe the normal human condition as being one in which most people live out their lives chained up at the bottom of a dark cave. The reality perceived by the inhabitants of the cave is limited to a view of distorted shadows projected on the opposite wall of the cave, which the prisoners habitually misinterpret. The exceptional person who escapes this bondage, and who climbs out of the cave, is at first dazzled by the sunlight but eventually learns to view a different, properly illuminated reality.
connect the ascent into the upper world and the sight of the objects there with the upward progress of the mind into the intelligible region . . . the final thing to be perceived in the intelligible region, and perceived only with difficulty, is the form of the good; once seen it is inferred to be responsible for whatever is right and valuable in anything, producing in the visible region light and the source of light, and being in the intelligible region itself the controlling source of truth and intelligence.
Plato also discusses the difficulties encountered by a person who returns to the cave after a sojourn in the light. Such a person has to learn once again to live in the dark and to successfully compete with other people at the bottom of the cave in an elaborate game of misinterpreting reality.
Nor will you think it strange that anyone who descends from contemplation of the divine to human life and its ills should blunder and make a fool of himself, if, while still blinded and unaccustomed to the surrounding darkness, he’s forcibly put on trial in the law-courts or elsewhere about the shadows of justice or the figures of which they are shadows, and made to dispute about the notions of them held by men who have never seen justice itself.
People who describe their mystical experiences can be divided into two types: those who were trained for the experience and those who were not. Training methods vary as widely as the mystical traditions that teach them, and are as various as the names of the final goal: ‘in all the great spiritual traditions is a relatively rare but universal and liberating experience either of self-oblivion or nirvana as in Buddhism or of a special relationship with the Deity, whether this remain unnamed or named as God, the Absolute, the Ultimate Reality, the All-Holy and Almighty, Cosmic Reality, the Ground of Being, the Transcendent or the One’.
Underlying them all is a fairly simple common principle: that normal human consciousness has evolved into an awareness of individual mortality, from which there is a need to escape. Somewhere in the distant ancestry of humanity a threshold of consciousness was crossed, since when individual humans have had to endure the constant anxiety about personal death. The ancients variously referred to the crossing of this threshold as a fall from grace, a descent from a Golden Age, or an eviction from a garden of easy living. Modern people are more likely to see it as an advancement or an evolutionary step, rather than a fall, which has provided the fundamental distinction between humans and other animals.
 F. C. Happold, Mysticism, p. 18.
 Margaret Smith, ‘The Nature and Meaning of Mysticism’, in Richard Woods, ed., Understanding Mysticism, p. 19.
 R. C. Zaehner, ‘Mysticism Sacred and Profane’, in Woods, ibid., pp. 56–77.
 Walter T. Stace, The Teachings of the Mystics, pp. 15–23.
 E. G. Brown, ‘A Year Among the Persians’, quoted in Smith, op. cit., p. 20.
 Plato, The Republic, pp. 320–1.
 Ibid., p. 321.
 Walter H. Principe, ‘Mysticism: its meaning and varieties’, in Harold Coward and Terence Penelhum, eds., Mystics and Scholars, p. 4.