An Argument for the Immorality of the Soul - Excerpt from Plato's "Phaedo"
-Compounded Versus Simple- and -Physical Versus Intellectual-
beauty, justice, quality are things that don't change with time. Whereas those physical things which participate in beauty are always changing and altering their nature. Thus it is clear that the physical things which can be sensed by the body change while those which can only be seen with the intellectual mind don't change. Thus there is a dual nature of things here, the "seen" and the "unseen."
Which then is the soul more like, the changing body or the unchanging ideas of the mind? Socrates makes it clear that the soul is more truly itself when it participates in the flight from the senses and retreat into the eternal ideas of the mind.
"But when returning into herself she reflects; then she passes into the realm of purity, and eternity, and immortality, and unchangeableness, which are her kindred, and with them she ever lives, when she is by herself and is not let or hindered; then she ceases from her erring ways, and being in communion with the unchanging is unchanging."
"Then reflect, Cebes: is not the conclusion of the whole matter this?-that the soul is in the very likeness of the divine, and immortal, and intelligible, and uniform, and indissoluble, and unchangeable; and the body is in the very likeness of the human, and mortal, and unintelligible, and multiform, and dissoluble, and changeable. Can this, my dear Cebes, be denied?"
Socrates makes a strong argument for the differing nature of the soul/mind and the body. To put it in a simpler way, we could summarize it like this:
1) The body is something physical.
2) Physical things are composed of parts and can therefore break apart.
3) Ideas are not physical things.
4) Ideas are not composed of parts and do not change.
5) The soul is more akin to the intellectual knowledge of ideas.
6) Therefore, the soul must itself be like those ideas, non physical and simple.
7) Therefore the soul will survive the death of the body and be eternal.