This work brings together Philip van der Eijk's previously published essays on the close connections that existed between medicine and philosophy throughout antiquity. Medical authors such as the Hippocratic writers, Diocles, Galen, Soranus and Caelius Aurelianus elaborated on philosophical methods such as causal explanation, definition and division and applied key concepts such as the notion of nature to their understanding of the human body. Similarly, philosophers such as Plato and Aristotle were highly valued for their contributions to medicine. This interaction was particularly striking in the study of the human soul in its relation to the body, as illustrated by approaches to specific topics such as intellect, sleep and dreams, and diet and drugs. With a detailed introduction surveying the subject as a whole and an essay on Aristotle's treatment of sleep, this wide-ranging and accessible collection is essential reading for the student of ancient philosophy and science.