Soul of the World (or Anima Mundi) is the key to our grasp of Yeats as a writer in the Hermetic tradition and that it underlies his whole sense of artistic tradition, I affirm that the right to primacy in any consideration of Yeats's major concept belongs to Anima Mundi. Through his vital, lifelong rapport with this Great Mind and Memory, Yeats communed with universal tradition. His desire to make the rapport a group effort, dependent upon collaborators, reinforced the notions of community and unity in multiplicity. Yeats believed that reality is discovered in the soul. For him, the Great Soul was a wellspring of imaginative art, a means by which Nature herself became intelligible. In this study, Yeats's theory of the World Soul, addressing occult, metaphysical, and literary antecedents of his belief, especially the way of his building of concept of "Anima Mundi" in his early life and experiences are surveyed. Yeats has a very keen interest in mysterious strange things in his early life, and he meets many influential friends who could help him build his theory of the World Soul in Dublin and London.