Margetts, who is a lecturer in psychiatry and in the history of medicine at McGill University, has happily combined his two interests in a study of the unconscious in the history of medical psychology. Almost since the dawn of civilization, man has had an inkling of mental activity outside of waking consciousness. Out of India, in the Upanishads, about 600 B.C., came the first clear idea of a stratified consciousness. Egypt contributed nothing of value that is known. The Greeks formulated some rather indefinite notions. From the age of the Greek philosophers to the renaissance, the gloom of the Dark Ages brought forth little that the Greeks had not already said. The renaissance developed a surge of insight into the nature of the unconscious, culminating in Schopenhauer (1788-1860) to whom Freud grants priority for the formulation of the theory of repression.1 After Schopenhauer,