Yeats had a lifelong interest in mysticism, spiritualism, occultism and astrology. He read extensively on the subjects throughout his life, became a member of the paranormal research organisation "The Ghost Club" (in 1911) and was influenced by the writings of Emanuel Swedenborg.
Scholars of poetry don’t often follow Yeats out onto the treacherous ground of his esotericism, and yet doing so is one of the main interpretative keys to the Yeatsian worldview.
In Spiritus Mundi, there is, according to William Butler Yeats, ''a universal memory and a muse of sorts that provides inspiration to the poet or writer.'' To Yeats, Spiritus Mundi is the source of all ''images'' and ''symbols,'' a ''collective unconscious.''
A Vision is the philosophical heart of all W.B. Yeats’ work during the 1920s and 1930s, lending theme and structure to Michael Robartes and the Dancer, The Tower, and The Winding Stair and Other Poems.
