This is an intellectual history of occult and esoteric currents in the English-speaking world from the early Romantic period to the early twentieth century. The Theosophical Society, founded in 1875 by Helena P. Blavatsky, holds a crucial position as the place where all these currents temporarily united, before again diverging. The book's ambiguous title points to the author's thesis that Theosophy owed as much to the skeptical Enlightenment of the eighteenth century as it did to the concept of spiritual enlightenment with which it is more readily associated.

The author respects his sources sufficiently to allow that their world, so different from that of academic reductionism, has a right to be exhibited on its own terms. At the same time he does not conceal the fact that he considers many of them deluded and deluding.

In the context of theosophical history, this book is neither on the side of the blind votaries of Madame Blavatsky, nor on that of her enemies. It may, therefore, be expected to mildly annoy both sides.