He created a complex system of spirituality, using the image of interlocking gyres (similar to spiral cones) to map out the development and reincarnation of the soul....
...He published his intricate theories of personality and history in A Vision in 1925 (which he substantially revised in 1937), and some of the symbolic patterns (gyres, moon phases) with which he organised these theories provide important background to many of the poems and plays he wrote during the second half of his career.--http://www.independent.ie/entertainment/books/wb-150/magic-myth-and-secrecy-wb-yeats-and-the-occult-31207213.html
We are entering," he said, "the political era, dominated by considerations of political necessity which belong to your people. That will be bad enough, but there will be worse to come. For after that there will be an age dominated by psychologists, which will be based on the complete understanding by everyone of all his own motives at every stage of his life. After that, there will be the worst age of all: the age of our people, the spiritualists. That will be a time when the separation of the living from the dead, and the dead from the living, will be completely broken down, and the world of the living will be in full communication with that of the dead.
Yeats expressed these ideas in a half-prophetic, half-humorous vein, and I may have distorted them in recording them. But certainly he spoke of the three ages to come, of the political, the psychological, and the spiritual: and he affirmed that the last would be "the worst". It is difficult to understand how to take such a prophecy. What is clear though, is that he saw spiritualism as a revolutionary social force as important in its power to influence the world, as politics, psychology, or science. (World Within World, 180–81)-- http://yeatsvision.blogspot.nl/