From Milton to Yeats, great poets have boldly asserted the truth of the imagination. In this study the force of their visionary thought is re-evaluated, and connections made between Milton or Shelley, Blake or Yeats, and modern esoteric ideas. Vision is understood not as speculation, but as truth to the whole range of human experience. Traditional forms of apocalypse and gnosis are also discussed in relation to literature. The author offers a new interpretation of Milton’s Paradise Lost and a discussion of the poet’s Christianity, orientations of the work of Blake and Shelley against a European background and a new theory of Yeats’ A Vision are included.