What is the Soul?
If it is to these realities--beauty, goodness, and so on--,that we refer all the
objects of the visible world, recollecting our former knowledge of them, then must it not
follow that our souls must exist before birth?
-Socrates, in Plato's Phaedo
Is the soul a physical part of the body, or is it a mental thing, like a thought? Some historians of philosophy credit Socrates with the first clear conception of the psyche, or soul. Socrates believed the soul to be the most essential part of a person, the element which is--like an idea-- eternal. But Socrates did believe that the soul goes through changes. Originally it dwells in the heaven of ideas but then is drawn down into the material world in which it inhabits the body of a person. As a child the soul remembers something of its past existence, but as a person grows older the soul becomes more and more attached to the body and to material things. When the person dies, the soul returns to the heaven of ideas, to the land of the dead, where it converses with other souls. But then after a time the soul decends to the physical world again and inhabits another body, and so on.
So Socrates believed in reincarnation. One of his proofs of this doctrine was his conception of knowledge as recollection. Everything we seem to learn in this world is really inside us already; we are reminded of the ideas by visible things. And there are clearly some things which we know, that we did not learn in this life. We know, for example, that all squares have four sides. We cannot know this from observation, for it would be impossible to observe every square there is or ever will be. If we cannot learn such a truth in this life, we must have learned it in some previous life! Therefore the soul must exist somewhere before it is born in a person.
So to Socrates the soul was not a thing or a substance, or even a faculty like hearing or sight, but rather something like one's character or personality or intelligence--not a "ghost" at all, but something very real. And so Socrates says that it is important to take proper care of the soul and make one's soul as good as possible, and this must be achieved through true philosophical knowledge of what goodness, truth, .justice, beauty, and so on, really are. To know that justice cannot mean harming others, and that in harming others you injure your own soul, is an example of the kind of knowledge which is crucial to the well-being of the soul. Socrates says that the only way you can really hurt a person is by making him a worse person. And so Socrates was not afraid of dying, but only of doing wrong and thereby doing violence to his own soul. Is there such a "thing" as a soul? Is it an idea?
Plato's Great Dialogues, New American Library, New York, 1956. See especially the Phaedo.