ABSTRACT
This introduction presents an overview of the key concepts discussed in this book. The aim of the book is to sketch an intellectual and moral picture-page, a spiritual costume-history of the last six centuries, showing at the same time the Platonic Idea of each age and the thought which inwardly inspired it and was its soul. This Thought of the Age is the organizing, the creative, the only truth in each age, although in actuality it is seldom seen in the pure state; for what happens is that the prism of the age breaks it up into a many-coloured rainbow of symbols. Only now and then is the age so fortunate as to produce the one great philosopher who reassembles the rays in the focus of his intellect. And this brings us to the real key of an age.
