T. S. Eliot has woven into the fabric of Four Quartets themes and symbols from a variety of Christian and non-Christian mystical sources. One of the powerful mystical elements is derived from the 16th century Spanish mystic, St. John of the Cross, whose spiritual exercises stand for the Negative Way. In the Western theology, there are two distinctive ways in which Christian saints or poets can perceive the Divine Reality. They are the Affirmative Way and the Negative Way. The Affirmative Way is the same idea with the doctrine or poetry of immanence, and the Negative Way with the doctrine or poetry of transcendence. T. S. Eliot's poetry is influenced by the tradition of the Negative Way or the poetry of transcendence. This thesis intends to study what characteristics the Affirmative Way or the Negative Way respectively has, and what is the theory of St. John's dark night of the soul. Also it wishes to trace which elements Eliot took from St. John and which elements he refused to take. Finally, in his masterpiece Four Quartets, this study will observe how St. John's negative theology is crystallized into the inner structure of the poem. Also this thesis wishes to reveal in what sense Eliot's poetry can be named the poetry of transcendence. Hopkins perceives the unity of nature, a poet and God, therefore he depicts the nature like "The world is charged with the grandeur of God." But Eliot is not eager to perceive the immanent presence of God in the power and beauty of nature. Instead, the poet is evoked with partial ecstasy and partial dread and goes through purgation process and afterwards reaches self-oblivion or union with God. In Eliot's idiom, he wishes to "go by a way wherein there is no ecstasy." In "Burnt Norton" III and "East Coker" III Eliot gives powerful expression to St. John's Negative Way. In these parts Eliot tries to apply St. John's theory, which was, originally, individual way of spiritual exercises, to diagnosing the collective spiritual darkness of modern London. Eliot seems to declare such a modern society must pass through the painful self-negation and complete deprivation, as shown in St. John's Negative Way. According to John X. Cooper, such idea of Eliot's is possibly true, because if the individual purification cannot bring us back from the abyss, the mere social world can hold absolutely no hope. We can hear Eliot's prophetic voice saying that after descending to the bottom and confronting the absolute solitude and abyss, the soul can arise from the dark night of purgation towards the world of light. Four Quartets, however, remains first and foremost a poem not a poetic version of mystical theology. Although Eliot alludes to and even paraphrases St. John's dark night of the soul, St. John's negative theology can be only one of the powerful threads in Eliot's poetical fabric.