Saint Augustine once remarked with respect to "time" that on one level he knows what it is, but if pressed to give a more exact definition, he finds himself a bit at a loss. Mysticism is like time. Some of the difficulties encountered in defining time appear in any attempt to be more precise about mysticism. The etymology of "mysticism" implies a connection to mystery, which in theological language further implies that we can never fathom it entirely. A general definition that has the virtue of covering traditions as diverse as Buddhism, Christianity, Hinduism, Islam, and Judaism is the attempt by humans to attain the ultimate reality of things and experience communion with the Highest. In The Varieties of Religious Experience, William James identified four "marks" of mystical experience that are reflected in much of his subsequent writing, both as elements of definitions and in the course of discussions of mysticism: ineffability, noetic quality, transiency, and passivity.
Ineffability: Since no adequate report of this kind of experience can be given in words, it follows that it must be directly experienced. In this respect, it is said to resemble feelings more than intellectual states. For example, you can tell someone about the experience of being in love, but there is no substitute for the firsthand experience. The mystic after the mystical experience is invariably incapable of describing what happened or even, it would seem, of remembering anything at all except that something did happen. The mystic often lacks the power to reflect articulately on the experience or to express it in apt forms of communication. Noetic quality: The comparison with feeling does not mean to suggest that mystical states are devoid of knowledge content. For example, you can know a person by being given a short biographical sketch of them, but you know them in a different way through the experience of loving them. Mystical theology is knowledge of God by experience, arrived at through the embrace of unifying love. The mystical experience is a vision of the world that is free, to a very unusual extent, from the interposition of concepts. There is obviously something nonmental, alogical, paradoxical, and unpredictable about the mystical phenomenon, but it is not, therefore, irrational or antirational or religion without thought. Rather, as Zen masters say, it is knowledge of the most adequate kind, only it cannot be expressed in words. Mysticism may be defined as belief in a third kind of knowledge, the other two being sense knowledge and knowledge by inference. The dominant aspects of this third type of knowledge are intuition and love.
Transiency: The feelings and aspects cannot be sustained for a long period of time. The mystical experience admits of various degrees, from short and rare divine or sacred "touches" to the practically permanent union with the One in the so-called mystical marriage. Passivity: Although one can take the initiative to more readily dispose oneself to receive mystical experience, the experience itself is experienced as independent of one's own efforts. Sometimes the mystical feels as if one were grasped and held by a superior power. For example, you can do things to be a more loving person, and one more capable of receiving love. But the decision by another to love cannot be coerced; it must come freely from them.
The emphasis placed on mysticism and the psychic phenomena of mysticism has varied according to time and place. In late 19th-century France, for example, great stress was placed on mystics, and they were regarded as defining criteria of genuine mysticism. Christian mysticism today, as formed by the works of Saint John of the Cross, is by no means composed of ecstasies, visions, and other extraordinary psychological phenomena. They are not essential to the mystical experience, and indeed are considered to be sometimes hindrances to its proper realization. In the higher states of spiritual marriage, they normally cease.
The union of contemplative and active elements in mysticism is of special note. The passivity associated with mystical experience does not preclude mystics from being persons of great initiative and energy. Mysticism need not be world destroying. Holiness does not mean a retreat from or rejection of the world. To be a mystic is not the same thing as being a spectator on the fence. On the other hand, over-involvement with the world can mean that the potential for contemplation either goes uncultivated or can be lost.
Both East and West have cultivated monastic traditions for the development of contemplation.
The many religious traditions differ on the degree of involvement with the world that is correlated with mystical contemplation. But all would agree that running away from the world is not the mystical way; the challenge is to make the mystical experience interfused with daily life and religious observance.
Mysticism is the art of union with reality. The mystic is a person who has attained that union in greater or less degree, or who aims at and believes in such attainment. A mystic is one who recognizes that prayer is a dialogue. It involves a give-and-take, a listening and speaking. The One speaks to us, we listen. We speak to the One, One listens. Prayer begins with the One, not with us. The One does not need prayer, we do. The listening element in prayer is usually the most important. Perseverance in prayer can consist in simply starting over once again, today and every day. Joy comes from being in the presence of the Other. Mysticism and mystical are simply about immediacy. A mystic is one who seeks an immediate union with the One without interference or mediation of objects, images, doctrines, thoughts, or ideas.