That is, a statue of Helen of Troy is considered beautiful by people because it derives its beautiful qualities from the Form of Beauty. Socrates then uses Simmias as an example to introduce the idea of carriers . If Simmias is both taller than Socrates but shorter than Phaedo, then be exhibits both tallness and shortness. The problem is that tallness is obviously not the same as shortness and it cannot be both tall and short as in the case of Simmias tallness. If one quality won t admit of another then it either flees when its opposite is present or is destroyed by its opposite.
Carriers are things that share the same properties of qualities as in the example of fire and heat.
Fire and water are carriers of heat and cold, respectively. All of this is analogous to the soul according to Socrates. He thinks now that he has adequately proven that the soul is that which makes the body live, so it can t admit of death. Therefore the soul is deathless, or immortal. The Phaedo ends with a Socrates saying that since the soul is immortal, it requires our care in life by being good so that we may fare well in death.