Which of these details figures prominently in the philosophy of William Butler Yeats? A. an intricate dance

B. periods of two thousand years

C. a marriage of heaven and hell

D. a dark cave

C). A marriage of heaven and hell.

Explanation:

Yeats had a preoccupation with the occult and mysticism. His poetry offers a fusion of the spiritual and supernatural. His attraction towards occult began he started studying 'Theosophy' which was developed through his involvement in a mystical secret society. His transcendentalism is reflected clearly through his discussion of the reincarnation and journey of the soul. His poems like 'The Second Coming', 'Sailing to Byzantium' reflects his interest in the occult. His poetry is deeply inspired by these interests. He himself states that '"If I had not made magic my constant study, I could not have written a single word of my black book ... ever have come to exist. The mystical life in the centre of all that I do and all that I think and all that I write." This idea is further explained in his work 'A Vision.' Thus, his philosophy prominently discusses the figure of 'a marriage between heaven and hell' as it adds to his spiritual and mystical vision. Therefore, option C is the correct answer.