Phaedo is a philosophical dialogue by the Ancient Greek philosopher Plato about Socrates' arguments for the soul's immortality. Shortly before his execution, Socrates makes four arguments for why the soul must be immortal: a cyclical theory that things are born of their opposites and that death and life are therefore dialectically interrelated, a recollection theory that humans possess innate knowledge at birth and therefore must have existed before and after corporeal life, and two other arguments that focus on the soul's immortality because of its participation in metaphysical forms.