Christian mysticism is the experiential and contemplative tradition within Christianity — the stream that emphasises direct encounter with God over doctrinal belief or ritual performance. From the Desert Fathers of 3rd-century Egypt who developed the first systematic practices of contemplative prayer, through the Rhineland mystics of the 14th century, to the Spanish mystics of the Counter-Reformation and the Quaker tradition of the inner light, Christian mysticism has consistently maintained that union with God is available to any human being willing to undergo the necessary purification and surrender.
In the 3rd and 4th centuries CE, thousands of men and women fled the cities of Egypt and Syria for the desert — not to escape the world but to face themselves without distraction. The Desert Fathers and Mothers developed the first systematic analysis of the inner life: the eight logismoi (thoughts/passions that obstruct prayer), the practice of hesychia (inner stillness), and the prayer of the heart that became the Jesus Prayer. Their sayings (Apophthegmata) remain among the most psychologically astute spiritual texts ever written.
Meister Eckhart (c.1260–1328) is the greatest speculative mystic in the Christian tradition and one of the most radical. His teaching that the ground of the soul (Seelengrund) is identical with the ground of God — that at the deepest level there is no distinction between the human and the divine — brought him to the edge of heresy and 28 propositions were posthumously condemned by Pope John XXII. His contemporary Hildegard von Bingen combined mystical vision with music, medicine, natural philosophy, and political courage in one of the most extraordinary medieval careers.
The Rhineland tradition — Eckhart, Tauler, Suso, and the anonymous author of the Theologia Germanica — shaped both Catholic contemplation and, through Luther's reading of the Theologia Germanica, Protestant spirituality. Its non-dual undercurrents continued through the Quakers, the Cambridge Platonists, and into contemporary Christian contemplation.
The eye through which I see God is the same eye through which God sees me. My eye and God's eye are one eye, one seeing, one knowing, one love. — Meister Eckhart