427-347 BC

Portrait of PlatoPlato was a renowned Greek philosopher. His teacher was Socrates, and he wrote much about what Socrates said. Plato founded a school in Athens in a grove sacred to the demigod Academus. It was called the Academy (which is where we get the word, academics). It was considered a university of higher learning which, at that time, included physical science, astronomy, and mathematics as well as philosophy.

Plato forwarded a theory of the body now known as pneuma theory. He saw life as involving three levels of pneuma or natural spirit or soul. All three levels arose from the vital organs. Inhaled air, emanating from God was transformed into the first form of pneuma. Another form of pneuma or natural spirit was in the veins, which moved with a tidal motion through the alimentary canal. When this venous fluid entered the heart it became transformed into a third, and higher form of pneuma, the "vital spirit." This enriched pneuma past to the base of the brain where it was again transformed into the highest form of pneuma—animal spirit. Animal spirit, the essence of life, was diffused through the body through hollow nerves.

Plato also believed in a tripartite division of the soul. One part was located in the head and was associated with intellect, a second in the heart and associated with anger, fear, and courage. The third part of the soul was in the liver where it was associated with lust, greed and desire.

Plato offered an elaborate interpretation of the parts and functions of the human body. In his late work, Timaeus, in which he sketched the outlines of nature, Plato saw the gods or "creative powers" as being the designers of the body:

The creative powers were aware of our tendency to excess. And so when they made the belly to be a receptacle for food, in order that men might not perish by disease, they formed the convolutions of the intestines, in this way retarding the passage of food through the body, lest mankind should be absorbed in eating and drinking, and the whole race become impervious to the divine philosophy.

I will now speak of the higher purpose of God in giving us eyes. Sight is the source of the greatest benefits to us; for if our eyes had never seen the sun, stars, and heavens, the words which we have spoken would not have been uttered. The sight of them and their revolutions has given us the knowledge of number and time, the power of enquiry, and philosophy, which is the great blessing of human life; not to speak of the lesser benefits which even the vulgar can appreciate. God gave us the faculty of sight that we might behold the order of the heavens and create a corresponding order in our own erring minds. To the like end the gifts of speech and hearing were bestowed upon us; not for the sake of irrational pleasure, but in order that we might harmonize the courses of the soul by sympathy with the harmony of sound, and cure ourselves of our irregular and graceless ways (Jowett, 478)

Logos is the Greek term meaning "the Word." Greek philosophers like Plato believed that speech flowed directly from the soul, and that the outer, spoken form of logos was a reflection of the inner logos of the soul. Plato used the term to refer not only to the spoken word but also of the unspoken word, the word still in the mind -- the reason. When applied to the universe, logos was taken to mean rational principles that govern all things. Plato viewed speech and hearing as arising from such rational principles associated with godlike powers and associated with moral behavior:

The gifts of speech and hearing were bestowed upon us; not for the sake of irrational pleasure, but in order that we might harmonize the courses of the soul by sympathy with the harmony of sound, and cure ourselves of our irregular and graceless ways. … (Jowett, 469).

I mean the conversation which the soul holds with herself in considering of anything. I speak of what I scarcely understand; but the soul when thinking appears to me to be just talking—asking questions of herself and answering them, affirming and denying. And when she has arrived at a decision, either gradually or by a sudden impulse, and has at last agreed and does not doubt, this is called her opinion. I say then, that to form an opinion is to speak, and an opinion is a word spoken, I mean to oneself and in silence, not aloud or to another (Plato Theaetetus 190 in Dialogues, Jowett, Vol 2, p. 193.

Plato defined hearing as a striking or series of strokes transmitted through the ears by air. It then travels by the blood to the brain and then to the liver, which houses the soul.

Writings of Plato

Jowett, Benjamin (1892) The dialogues of Plato (translated into English with analyses and introduction). (These passages were taken from Timaeus, in Jowett's third edition, volume 3. Translated in 1892.)

Writings about Plato

Critchley, MacDonald (1958). A critical survey of our conceptions as to the origins of language. In F. N. L. Poynter (Ed.) The history and philosophy of knowledge of the brain and its functions. (pp. 45-72). London.