Janus is both a summing up and continuation of Koestler's work over the past twenty-five years, since he turned from politics to the sciences of life- or more precisely, to the 'evolution, creativity and pathology of the human mind'. The insights gained on that long journey are here assembled in a coherent and comprehensive synthesis, and in the last part of the book, he offers us a tantalizing 'glance through the key-hole' from subatomic physics to metaphysics.