Aristotle on the Brain 13, 14)

HISTORY OF NEUROSCIENCE this light was necessary for vision (11, Aristotle on the Brain 13, 14). This idea that the eye contains light became the basis of theories of vi- CHARLES G. GROSS sion that persisted beyond the Renais- sance. Indeed, Alcmaeon’s idea of light in the eye was only disproved in the middle the Aristotle argued that the heart was the center of sensation and movement. By contrast, of eighteenth century (15). his predecessors, such as Alcmaeon, and his contemporaries, such as the Hippocratic Among the other pre-Socratic philos- doctors, attributed these functions to the brain. This article examines Aristotle’s views on opher-scientists who adopted and ex- brain function in the context of his time and considers their subsequent influence on the panded on Alcmaeon’s view of the func- development of the brain sciences. The Neuroscientist 1:245-250,1995 tions of the brain were Democritus, Anaxagoras, and Diogenes (10, 13, 14, KEY WORDS Aristotle, History of science, Greek science, Localization of function 16). Democritus developed a version that became very influential because of its on Plato. Democ- Aristotle’s name is invariably linked to ence of Aristotle on the subsequent de- impact Specifically, philosophy; indeed, for centuries, he velopment of the brain sciences. ritus taught that everything in the uni- verse is made of atoms of a was known as &dquo;The Philosopher.&dquo; Figures 1 and 2 provide some orienta- up particular size and The mind, However, he was also the leading bi- tion in time and space for this article. shape. psyche (soul, vital is made of the ologist of classical antiquity and one of principle) up lightest, the greatest biologists of all time. He Alcmaeon of Croton most spherical and fastest moving atoms. Although the psychic atoms are is usually considered the founder of Formal science, the idea that the uni- the first dispersed among other atoms throughout comparative anatomy, embry- verse is a complicated mechanism work- the first the first the body, they are much more numerous ologist, taxonomist, ing according to fixed laws that could be evolutionist, the first in the brain. Slightly cruder atoms are biogeographer, understood through human reason, be- and the first student of ani- concentrated in the heart, making it the systematic gan with the pre-Socratic philosopher- center of emotion, and still cruder ones mal behavior ( 1-4, but cf. 5). Not only scientists Thales, Anaximander and An- are located in the liver, which conse- was he important to the development aximenes in sixth-century BCE Miletus, of but was im- quently is the seat of lust and appetite. biology, biology very a Greek city in Asia Minor (1, 9). By the in his own as a This trichotomy developed into Plato’s portant development middle of the fifth century, there were thinker. Over a of his hierarchy of the parts of the soul in quarter writings three major centers of Greek medical were on and his which there is no question about the su- biology, biological science: Croton, in what is now southern work was crucial in him premacy of the brain. As he put in the distancing Italy, Agrigentum on the south coast of from his teacher, Plato Timaeus (17), &dquo;It is the divinest part of (6-8). Beyond modem Sicily, and Cos, an island off was a true us and lord over all the rest.&dquo; Then, in biology, he universal ge- modem Turkey. The oldest of these with Galen’s medical the three nius, writing permanent impact medical centers was in Croton, and its theorizing, on such as became the three of subjects logic, metaphysics, most famous member was Alcmaeon. soul-parts pneumas art, theater, economics, humoral physiology that dominated med- psychology, Croton was also the site of the Pythag- and His ical for so many centuries ( 18,19). politics. formerly dominating orean brotherhood, and there seems to thought Alcmaeon’s view of the he- influence on the physical and biologi- have been considerable interaction be- However, cal has dis- of the brain was not universal sciences, however, largely tween the Pythagoreans and the medical gemony appeared in the last several centuries. school ( 10-12). among the pre-Socratic philosopher-sci- Aristotle’s most entists. For the Perhaps egregious Alcmaeon was the first writer to example, Empedocles, scientific error fell in the domain we member of the medical center at champion the brain as the site of sensa- leading now call neuroscience: he that the blood was systemati- tion and cognition. He also seems to Agrigentum, taught denied the role of the the medium of and the cally controlling have been the first practitioner of ana- thought, degree brain in sensation on and movement, giv- tomic dissection as a tool of intellectual of intelligence depended the compo- this function to the heart. ing, instead, inquiry. His most detailed dissections sition of the blood (14, 16). Thus, for I consideration of this the heart was the central of begin enigma by and theories were on the senses, partic- him, organ summarizing the views on brain func- ularly vision. Alcmaeon described the intellect and the seat of mental disorder. tion held the Greek The idea of the heart as the by philosopher-sci- optic nerves, noted that they &dquo;came to- general entists before Aristotle. Then, the ar- gether behind the forehead&dquo; (which is seat of intelligence and emotion was not and evidence Aristotle guments put why, he opined, the eyes move together) new. It had been held in many earlier forward for his curious views are pre- and suggested that they were &dquo;light- cultures such as the Egyptian, Mesopo- sented. I examine the influ- Finally, bearing paths&dquo; to the brain. He removed tamian, Babylonian, and Indian (20, 21). and dissected the eye, and observed that It is reported to be common among non- From the Department of Psychology, Pnnceton it contained water. Observations of what literate cultures as well (20), as illus- New University, Pnnceton, Jersey. are now called phosphenes after a blow trated by the oft-quoted remark of a Address reprint requests to: C. G. Gross, Dept. to the led him to conclude that the Pueblo chief to C.G. &dquo;I know of Psychology, Pnnceton University, Pnnceton, NJ eye Jung (22), 08544. eye also contained light (fire) and that you white men think with the brain. That Volume 1, Number 4, 1995 245 Copyright © 1995 by Williams & Wilkins ISSN 1073-8584 Fig. 1. accounts for your shortcomings. We red pre-Socratic thinkers in general, they re- functions of the brain, he is equally men think with the heart.&dquo; Ancient Chi- jected supernatural causes of disease and clear: nese medicine had rather more compli- sought natural explanations through ob- It ought to be generally known that the cated views than the relatively simple servation and extended case studies (1, source of our pleasure, merriment, heart-centered ones of other ancient 10, 12). Similarly detailed accounts of laughter, and amusement, as of our grief, cultures, but it also disease were rare until after thoroughly ignored processes pain, anxiety, and tears, is none other the brain In the role of the (23, 24). fact, the Renaissance and even then tended to than the brain. It is specially the organ brain in perception and cognition did not be advertisements for the skill of the which enables us to think, see, and hear, enter Chinese thought until the Jesuit physician rather than empirical studies. and to distinguish the ugly and the beau- Matteo Ricci’s treatise (in 1595, in Chi- The Hippocratic work of greatest rel- tiful, the bad and the good, pleasant and It is the brain nese) on the art of memory, which he evance to brain function is the famed es- unpleasant.... too which is the seat of madness and delir- wrote as part of his campaign to convert say &dquo;On the Sacred Disease&dquo; (27), ium, of the fears and which assail the scholar class (25). which is epilepsy. The work, probably frights us, often by night, but sometimes even designed as a lecture for laymen, opens The Hippocratic Doctors by day; it is there where lies the cause with an homage to reason and the rejec- of insomnia and sleep-walking, of The third center for the great teaching tion of superstition: thoughts that will not come, forgotten and practice of medicine in the fifth cen- duties, and eccentricities. tury BCE was the island of Cos, and its I do not believe that the Sacred Disease he neither the dia- most famous member was Hippocrates. is any more divine or sacred than any Furthermore, states, The first large body of Western scientific other disease, but, on the contrary, has phragm nor the heart has any mental writings that have survived is the Hip- specific characteristics and a definite functions, as some have claimed: ’new- cause.... of these takes in pocratic corpus. Although there is no ther organs any part It is that those who first which are question that Hippocrates was a real his- my opinion mental operations, completely called this disease ’sacred’ were the sort torical figure, it is not clear which of the undertaken by the brain.&dquo; of we now call witch-doctors, called were actu- people What then is the cause of epilepsy, the writings Hippocratic faith-healers, quacks, and charlatans. written him (26). The so-called sacred disease? He goes on to ally by Hippo- These are exactly the people who pre- cratic consists of more than 60 say that it attacks only the phlegmatic, corpus tend to be very pious and to be particu- which in those with an excess of phlegm or treatises, vary enormously style larly wise.

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