There is little of Mysticism in the first schools of Greek philosophy, but it already takes a large place in the system of Plato, e.g., in his theory of the world of ideas, of the origin of the world soul and the human soul, in his doctrine of recollection and intuition. The Alexandrian Jew Philo (30 B.C-A.D. 50) combined these Platonic elements with the data of the Old Testament, and taught that every man, by freeing himself from matter and receiving illumination from God, may reach the mystical, ecstatic, or prophetical state, where he is absorbed into the Divinity. The most systematic attempt at a philosophical system of a mystical character was that of the Neoplatonic School of Alexandria, especially ofPlotinus (A.D. 205-70) in his "Enneads". His system is a syncretism of the previous philosophies on the basis of Mysticism--an emanative and pantheistic Monism. Above all being, there is the One absolutely indetermined, the absolutely Good. From it come forth through successive emanations intelligence (nous) with its ideas, the world-soul with its plastic forces (logoi spermatikoi), matter inactive, and the principle of imperfection. The human soul had its existence in the world-soul until it was united with matter. The end of human life and of philosophy is to realize the mystical return of the soul to God. Freeing itself from the sensuous world by purification (katharsis), the human soul ascends by successive steps through the various degrees of the metaphysical order, until it unites itself in a confused and unconscious contemplation to the One, and sinks into it: it is the state of ecstasis.
With Christianity, the history of Mysticism enters into a new period. The Fathers recognized indeed the partial truth of the pagan system, but they pointed out also its fundamental errors. They made a distinction between reason and faith, philosophy and theology; they acknowledged the aspirations of the soul, but, at the same time, they emphasized its essential inability to penetrate the mysteries of Divine life. They taught that the vision of God is the work of grace and the reward of eternal life; in the present life only a few souls, by a special grace, can reach it. On these principles, the Christian school of Alexandria opposed the true gnosis based on grace and faith to the Gnostic heresies. St. Augustine teaches indeed that we know the essences of things in rationibus aeternis (in the eternal reasons), but this knowledge has its starting point in the data of sense (cf. Quæstiones, LXXXIII, c. xlvi). Pseudo-Dionysius, in his various works, gave a systematic treatment of Christian Mysticism, carefully distinguishing between rational and mystical knowledge. By the former, he says, we know God, not in His nature, but through the wonderful order of the universe, which is a participation of the Divine ideas ("De Divinis Nomin.", c, vii, §§ 2-3, in P.G., III, 867 sq.). There is, however, he adds, a more perfect knowledge of God possible in this life, beyond the attainments of reason even enlightened by faith, through which the soul contemplates directly the mysteries of Divine light. The contemplation in the present life is possible only to a few privileged souls, through a very special grace of God: it is the theosis, mystike enosis.
Christian mysticism advocates teaches that for Christians the major emphasis of mysticism concerns a spiritual transformation of the egoic self, the following of a path designed to produce more fully realized human persons, "created in the Image and Likeness of God" and as such, living in harmonious communion with God, the Church, the rest of humanity, and all creation, including oneself. For Christians, this human potential is realized most perfectly in Jesus, precisely because he is both God and human, and is manifested in others through their association with him, whether conscious, as in the case of Christian mystics, or unconscious, with regard to spiritual persons who follow other traditions, such as Gandhi. The Eastern Christian tradition speaks of this transformation in terms of theosis or divinization, perhaps best summed up by an ancient aphorism usually attributed to Athanasius of Alexandria: "God became human so that man might become god."
Going back at least to Evagrius Ponticus and Pseudo-Dionysius, Christian mystics have pursued a threefold path in their pursuit of holiness. While the three aspects have different names in the different Christian traditions, they can be characterized as purgative, illuminative, and unitive, corresponding to body, soul (or mind), and spirit. The first, the way of purification, is where aspiring Christian mystics start. This aspect focuses on discipline, particularly in terms of the human body; thus, it emphasizes prayer at certain times, either alone or with others, and in certain postures, often standing or kneeling. It also emphasizes the other disciplines of fasting and alms-giving, the latter including those activities called "the works of mercy," both spiritual and corporal, such as feeding the hungry and sheltering the homeless.
Purification, which grounds Christian spirituality in general, is primarily focused on efforts to, in the words of St. Paul, "put to death the deeds of the flesh by the Holy Spirit" (Romans 8:13). The "deeds of the flesh" here include not only external behavior, but also those habits, attitudes, compulsions, addictions, etc. (sometimes called egoic passions) which oppose themselves to true being and living as a Christian not only exteriorly, but interiorly as well. Evelyn Underhill describes purification as an awareness of one's own imperfections and finiteness, followed by self-discipline and mortification. Because of its physical, disciplinary aspect, this phase, as well as the entire Christian spiritual path, is often referred to as "ascetic," a term which is derived from a Greek word which connotes athletic training. Because of this, in ancient Christian literature, prominent mystics are often called "spiritual athletes," an image which is also used several times in the New Testament to describe the Christian life. What is sought here is salvation in the original sense of the word, referring not only to one's eternal fate, but also to healing in all areas of life, including the restoration of spiritual, psychological, and physical health.
It remains a paradox of the mystics that the passivity at which they appear to aim is really a state of the most intense activity: more, that where it is wholly absent no great creative action can take place. In it, the superficial self compels itself to be still, in order that it may liberate another more deep-seated power which is, in the ecstasy of the contemplative genius, raised to the highest pitch of efficiency. Mysticism: A Study in Nature and Development of Spiritual Consciousness... by Evelyn Underhill
The second phase, the path of illumination, has to do with the activity of the Holy Spirit enlightening the mind, giving insights into truths not only explicit in scripture and the rest of the Christian tradition, but also those implicit in nature, not in the scientific sense, but rather in terms of an illumination of the "depth" aspects of reality and natural happenings, such that the working of God is perceived in all that one experiences. Underhill describes it as marked by a consciousness of a transcendent order and a vision of a new heaven and a new earth.
The third phase, usually called contemplation in the Western tradition, refers to the experience of oneself as in some way united with God. The experience of union varies, but it is first and foremost always associated with a reuniting with Divine love, the underlying theme being that God, the perfect goodness, is known or experienced at least as much by the heart as by the intellect since, in the words 1 John 4:16: "God is love, and he who abides in love abides in God and God in him." Some approaches to classical mysticism would consider the first two phases as preparatory to the third, explicitly mystical experience, but others state that these three phases overlap and intertwine.
Author and mystic Evelyn Underhill recognizes two additional phases to the mystical path. First comes the awakening, the stage in which one begins to have some consciousness of absolute or divine reality. Purgation and illumination are followed by a fourth stage which Underhill, borrowing the language of St. John of the Cross, calls the dark night of the soul. This stage, experienced by the few, is one of final and complete purification and is marked by confusion, helplessness, stagnation of the will, and a sense of the withdrawal of God's presence. This dark night of the soul is not, in Underhill's conception, the Divine Darkness of the pseudo-Dionysius and German Christian mysticism. It is the period of final "unselfing" and the surrender to the hidden purposes of the divine will. Her fifth and final stage is union with the object of love, the one Reality, God. Here the self has been permanently established on a transcendental level and liberated for a new purpose.
Another aspect of traditional Christian spirituality, or mysticism, has to do with its communal basis. Even for hermits, the Christian life is always lived in communion with the Church, the community of believers. Thus, participation in corporate worship, especially the Eucharist, is an essential part of Christian mysticism. Connected with this is the practice of having a spiritual director, confessor, or "soul friend" with which to discuss one's spiritual progress. This person, who may be clerical or lay, acts as a spiritual mentor.