Along with the Republic and the Symposium, Plato's Phaedo is one of the
three important works of ancient Greek philosophy. The discussion is
given from the viewpoint of Phaedo of Elis, a pupil of Socrates who was
there when he died. The debate from that day is related by Phaedo to the
Pythagorean philosopher Echecrates. The Cyclical Argument, also known as
the Opposites Argument, argues that since Forms are timeless and
unchangeable and since the soul continuously sustains life, it must not
expire and is thus ineluctably "imperishable." The soul must be the
indestructible opposite of the body since the latter is mortal and prone
to physical death. Plato then offers the comparison of cold and fire.
According to the Theory of Recollection, humans are born with some
non-empirical information, which implies that the soul existed before
birth to store that knowledge. Another explanation of the notion may be
found in Plato's Meno, albeit Socrates makes less strong claims in Meno
than he does in Phaedo. The Affinity Argument demonstrates how things
that are unseen, eternal, and incorporeal differ from those that are
visible, mortal, and corporeal. Since the soul is a component of the
Form of Life by nature, it is immortal and cannot pass away.
