The present thesis proposes to explore W. B. Yeats’s inner dialogue with his predecessor William Blake, as “other” or spiritual counterpart who guides the ego-consciousness of the poet into the realm of the unconscious. The “occult”/arcane relationship of the two poets will be examined within the theoretical framework of C. G. Jung’s depth/analytical psychology. It is recorded that Yeats associated Blake’s unconventional, highly imaginative art of intricate symbolism with his own life-long interest in the occult, as expressed through his initiation into theosophy, magic, alchemy and spiritualism. There is also evidence of Yeats regarding Blake’s “presence” at a seance, as one of his “spirit-guides” that have influenced his work. In the introduction, I explain that Jungian psychology provides an appropriate analytical tool or “meta-language” for interpreting Yeats’s artistic duality in terms of Blake’s visionary work, by using a language of symbols/archetypal images that describe the world of the unconscious. Jungian and post-Jungian critics, such as P. W. Martin, Susan Rowland, Christopher Hauke and others, have contributed to a revival in Jungian literary and cultural criticism, by accepting the existence of a “psychic reality,” where “psyche” stands for all conscious and unconscious mental operations, a fundamental concept of Jungian psychology. The first chapter deals with Blake’s role as an inner, guiding voice emerging through the analysis of paradoxical friendships in Yeats’s initiation-patterned stories from his prose collection The Secret Rose, which are related to the Jungian “process of individuation.” In the second chapter, Yeats’s pursuit of his daimon or “other” is related to Hermeticist Ribh’s ecstatic vision of God as featured in his poetry collection Supernatural Songs. Ribh is also juxtaposed to ethereal Thel, Blake’s persona in his poem The Book of Thel. In the third chapter, Jung’s technique of “alchemical active imagination” is borrowed to interpret Blake’s poem “The Mental Traveller” in relation to Yeats’s “The Double Vision of Michael Robartes.” In the last chapter, Blake’s play The Ghost of Abel provides the background material for interpreting Yeats’s dramatized appearances of a ghost and a spirit in his plays The Resurrection and The Words Upon the Window-Pane that deal with the spiritual “other” and its problematic reception by the skeptical world.