Plato’s “Phaedo” is a dialogue between Socrates and his friends, Cebes and Simmias. These two men have asked Socrates to prove to them that the soul survives after death due to its immortality. Socrates gives them several arguments, which ultimately lead to his conclusion that proves the soul’s immortality and furthermore its perishability. Socrates proves that soul lives despite the body’s death by showing that if an entity has a certain characteristic, it will not accept the characteristic that is the opposite to its own.
Socrates believes that the soul and the body are two entirely different things; the body is created to disappear after death and the soul is created to exist forever after death. The first argument that Socrates uses to explain the soul’s immortality uses snow and fire. He explains to Cebes and Simmias that snow possesses the characteristic of cold, whose opposite is heat. When snow, “…is under the influence of heat… the snow will either retire of perish… And the fire too at the advance of cold will either retire or perish” (Plato 1).
Socrates clarifies that snow cannot accept the opposite of its characteristic, cold, which is heat. When heat approaches the snow, the entity that possesses coldness, this entity must either retire or perish. It is not possible that snow can remain the same even when being approached by heat because snow is cold. The same is true for when cold approaches fire, which possesses heat. When cold approaches the hot fire, the fire cannot exist anymore and must either retire or perish. Socrates’ second example consists of odd and even numbers.
He explains that due to the number three’s oddness, it can never be even. Socrates states that entities will, “… reject the idea which is opposed to that which is contained in them, and when it approaches them they either perish or withdraw” (Plato 2). He clarifies that as long as three remains the number three, it will possess oddness and can therefore never be even, as “…the idea of the even number will never arrive at three” (Plato 3). If the form of evenness approaches the number three, it must either perish or withdraw.
Similar to his example of the snow and fire, Socrates elucidates again that an entity cannot have a characteristic that is the opposite to the one it already possesses and if this opposite approaches said entity, the entity will either die or retire. Following these two examples, Socrates concludes with the explanation of the soul’s imperishability. He reiterates his point that something cannot accept its characteristic’s opposite by stating that, “…not only opposites will receive opposites, but also that nothing which brings the opposite will admit the opposite of that which it brings, in that to which it is brought” (Plato 3).
He says that one of the characteristics that the soul possesses is life, which is the opposite of death, so, “…the soul, as has been acknowledged, will never receive the opposite of what she brings” (Plato 3). Socrates explains that the soul can never admit death because it possesses a quality that is death’s opposite. When death approaches the soul, according to his previous arguments, it would either retire or perish; however, “…the soul when attacked by death cannot perish” (Plato 4) because the soul cannot admit death.
He believes that when death comes to a man, his body dies, but his soul is preserved (Plato 5). Socrates proves that the soul will not admit death and when it is approached by death, it will not perish, but retire to another world. Socrates shows that an entity will not accept the opposite to a form that it possesses, which leads him to his proof of the soul’s immortality. He explains that just as snow cannot admit heat and the number three cannot admit evenness, the soul cannot admit death. Just as something that is bitter cannot be sweet, the soul cannot perish because it possesses life.