The Christian mystical tradition is one of the least known and deepest contemplative lineages in history. It was suppressed again and again by the institutional Church, kept alive at great personal cost by mystics working at the edges, and has only recently returned to wider awareness through teachers like Thomas Keating, Thomas Merton, Richard Rohr, and Cynthia Bourgeault. It begins in the Egyptian desert of the 4th century, with the Desert Fathers and Mothers, Christian monks who fled to the desert to seek a direct experience of God, away from the increasingly bureaucratic imperial Church. Evagrius of Pontus (345 to 399 CE) organized their approach in writings that shaped all later Christian mysticism: the goal is hesychia (stillness, silence, calm), and the method is bringing your attention back, again and again, to God, in a prayer that goes past words and concepts. In this tradition the heart is not a metaphor. It is the organ of spiritual perception, the deepest center of the person, where you meet God.
The high point of Western Christian mysticism is the 16th-century Spanish tradition of Teresa of Ávila and John of the Cross. Teresa's 'Interior Castle' (1577) pictures the soul as a crystal globe with seven mansions, and God dwelling in the innermost one. The contemplative life is a journey inward through these mansions, past distraction, dryness, spiritual pride, and the dark night of the soul, toward union in the final mansion. Her account of the stages of prayer, vocal prayer, mental prayer, the prayer of recollection, the prayer of quiet, the prayer of union, and finally the spiritual marriage, is the most psychologically precise map of contemplative growth in the Western tradition. John of the Cross, her confessor and collaborator, describes in 'The Dark Night of the Soul' a stretch of deep spiritual desolation, when all sense of comfort is withdrawn, that often comes with the deepest stages of practice. Other traditions know it too, from Buddhist 'dark nights' to the Sufi stations of contraction.
Centering Prayer is a modern form of Christian contemplative practice developed by the Trappist monks Thomas Keating, Basil Pennington, and William Meninger at St. Joseph's Abbey in Spencer, Massachusetts, starting in the 1970s. Drawing on 'The Cloud of Unknowing' (an anonymous 14th-century English mystical text), on John of the Cross, and on the Desert Fathers, Keating built Centering Prayer as an easy way for ordinary Christians to enter the contemplative side of their own tradition. The method has four simple guidelines: choose a sacred word as a symbol of your intention to consent to God's presence and action within you; sit comfortably with your eyes closed, settle briefly, and silently bring in the sacred word; whenever you notice thoughts, return ever so gently to the sacred word; at the end, stay in silence with your eyes closed for a couple of minutes. The sacred word, 'Jesus,' 'Abba,' 'Peace,' 'Love,' 'God,' is not a mantra to concentrate on. It is a gesture of consent, used only when thoughts pull you away, then let go of again.
What Centering Prayer shares with TM and other mantra traditions is the use of a word or sound to move beneath the surface of ordinary mental activity. You do not think about the word. You use it to come back when you get distracted. What sets it apart is its framework of relationship: you are not chasing a state of consciousness, you are opening to a presence. The silence is not empty. It is full, full of divine presence. Keating's idea of 'the Divine Therapy' holds that the deep rest of Centering Prayer lets buried emotional material, what he calls 'the unconscious,' rise up and be released, much as yoga nidra and Vipassana describe old psychological material surfacing and dissolving. The contemplative tradition already knew, in different words, what the neuroscientists are starting to document.