Rudolf Steiner had said that this book is not a history of mysticism. The book deals with a problem that had occupied him for many decades and which today has become a fundamental problem for all of humanity: the impact of modern scientific thinking on the experiences of inner spiritual life of man. In the conflict between reason and revelation, which reached its highest point in the 19th century but had begun much earlier, Steiner saw the seed of an even greater conflict that was to come, a conflict that includes the struggle of humanity against the subhuman point of modern technological developments.