Nemesius of Emesa

390- AD

Nemesius of Emesa (a Syrian town now called Homs) was a fourth-century Syrian physician and bishop. His main work, On the Nature of Man, written about 400 AD contained a detailed description of Galenic anatomy and physiology.

Nemesius believed that the faculties operated through the agent of an animal spirit produced after it had been carried through a network of arteries. This network was referred as the Rete Mirabile and is located at the base of the brain. Nemesius' doctrine of Ventricle localisation of mental functions was greatly acknowledged following its development, but it was later attacked.

Building upon the ventricle theory promoted by Galen, Nemesius theorized on loss of functions in brain damage by assigning different functions to each of the four ventricles in the brain. He placed perception and imagination in the two anterior lateral ventricles, cognition or intellectual abilities in the middle ventricle, and memory in the posterior ventricle.

The functions of the three ventricles on Nemeisus are similar to later information processing theories. In the anterior ventricles, sensation and perception were held together by a force that Nemesius identified as the faculty of imagination. The functioning of the middle ventricle, where he located the faculty of intellect, involved taking the sensory perceptions from the anterior areas and judging them. In the posterior faculty, the one associated with memory, the processed perceptions were stored.

Nemesius believed that the faculties operated through the agent of an animal spirit produced after it had been carried through the Rete Mirabile in the base of the brain. Later, however, when attempting to explain why the sense organs are arranged in pairs, Nemesius wrote: "For this reason [The Creator] made there to be two ventricles in the front, only, of the brain, so that the sensory nerves running from each ventricle should constitute the sense organs in pairs" (p. 332). That is, Nemesius said that imagination was located in the frontal lobes, but sensation was handled in the front ventricles.

Still later, Nemisius said:

The organ of [memory] is the hinder part of the brain (called also the cerebellum and hinder-brain) and the vital spirit there contained. Now if we make this assertion, that the senses have their sources and roots in the front ventricles of the brain, that those of the faculty of intellect are in the middle part of the brain, and that those of the faculty of memory are in the hinder brain, we are bound to offer demonstration that this is how these things work …(p. 341)

Nemesius was also well known for his theory of a five-tiered hierarchy of Divine Providence. One tier included the supreme God and involves God's control of the heavens and rational souls, another had to do with demon's control over the actions of man.

Writings by Nemesius

Nemesius (1955). The nature of man. Translated by W. Telfer (Ed.), Cyril of Jerusalem and Nemesius of Emesa. Philadelphia: Westminster Press.

Writings about Nemesius

Bennett, M.R. (2003) The early growth of neuro-scientific knowledge: the integrative action of the nervous system. In M. R. Bennett and P. M. R. Hacker Philosophical foundations of neuroscience (pp. 21-22 on Nemesius). NY: Wiley (Blackwell).