"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 mind 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 part of one great memory, the memory of Nature herself.
(3) That this great mind and great memory can be evoked by symbols."
---William Butler Yeats, "Magic" (1901)