Yeats’s occult philosophy was set forth in his 1901 essay “Magic.” Although it was much elaborated in A Vision (1925), it was never rescinded:

I believe in the practice and philosophy of what we have agreed to call magic, in what I must call the evocation of spirits, though I do not know what they are, in the power of creating magical illusions, in the visions of truth in the depths of the mind when the eyes are closed; and I believe in three doctrines, which have, as I think, been handed down from early times, and been the foundations of nearly all magical practices. These doctrines are --

(1) That the borders of our minds are ever shifting, and that many minds can flow into one another, as it were, and create or reveal a single mind, a single energy.

(2) That the borders of our memories are as shifting, and that our memories are a part of one great memory, the memory of Nature herself.

(3) That this great mind and great memory can be evoked by symbols.