Nemesius of Emesa

Nemesius was bishop of Emesa in Syria, the city now called Homs, at the end of the fourth century. Practically nothing is known about his life beyond the one book he left, which is titled On the Nature of Man and was written around 390 to 400.

The book is unusual, and it was influential far out of proportion to its author's fame.

Most Christian writing about human beings in that period starts from Genesis and stays with theology. Nemesius starts there too, man made in the image of God, standing on the border between the visible and invisible worlds, a creature who belongs to both, but then he does something few of his contemporaries did. He works through the body with the medical writers in hand. He knows Galen thoroughly, and Hippocrates, and the anatomical debates of the Greek physicians. He discusses the elements, the four humours, digestion, the pulse, respiration, generation, sleep, and the senses one by one, giving the physical account and then asking what it means that a soul lives in a body like this.

His treatment of the brain is the part historians cite most. Nemesius assigns imagination to the front ventricles of the brain, reason to the middle, and memory to the back, the earliest clear statement of the doctrine of the cerebral localisation of the faculties, which then held the field in Western medicine for well over a thousand years. Some scholars have also credited him with an early hint of the circulation of the blood, though that reading is contested and probably reads more into him than he says.

The theological core of the book is the union of soul and body. Nemesius refuses to say that the soul merely uses the body as a tool, and refuses to say that it is simply mixed into it. He argues for a real union in which each keeps its own nature, and he says openly that this is the same kind of union the church confesses in Christ. That argument, written a generation before the great christological councils, is why later theologians kept the book.

They kept it hard. On the Nature of Man was translated into Armenian, Arabic, and Georgian, and twice into Latin in the Middle Ages. Much of it was absorbed almost verbatim by John of Damascus into his own great summary of the faith, and through him it reached the whole Byzantine world. In the Latin West it circulated for centuries under the name of Gregory of Nyssa, and Thomas Aquinas quotes it that way.

On the question of the soul's origin Nemesius held, with Origen, that souls exist before bodies, a position the later church rejected, and one of the few points where readers pushed back on him.

Sources: Nemesius of Emesa, On the Nature of Man (English translation by R. W. Sharples and P. J. van der Eijk, Translated Texts for Historians); William Telfer, Cyril of Jerusalem and Nemesius of Emesa (Library of Christian Classics); the 1913 Catholic Encyclopedia.