This book traces the intellectual revolution initiated by Thales in the sixth century BC to its culmination in the metaphysics of Parmenides.

Reviewing his life's work in several areas, Koestler shows that the development of human intelligence mirrors the hierarchical order of the universe, examines links between creativity and humor, science, and art, and criticizes the behaviorist theory of cultural evolution.

In this classic work David Bohm, writing clearly and without technical jargon, develops a theory of quantum physics which treats the totality of existence as an unbroken whole.