Socrates returns to the subject of poetry and imitative art. Imitation is three steps from the Forms and truth. Artists seem to create things, but they really only create poor copies of the Ideas. Art imitates the specifics, but not the universal and ideal. An artist who paints a picture of a bed only makes a copy of a copy of the Idea or Form of a bed. The painter's knowledge is less than that of the person who want to use the thing he paints. The user of a harness knows more about its use than even the harness maker. Socrates bans imitative poets from the city because they tend to tell immoral stories and falsehoods.
Socrates says a just life's chief reward comes in the after life. Glaucon asks if Socrates believes the soul lives on after the body. Socrates argues that the soul cannot be destroyed by its particular evil, as other things are, since death does not make one more unjust. Death is not an evil, so it cannot destroy the soul. The soul then is immortal.
Even Tyrants do not destroy their soul, though they are nothing but unjust.
Socrates turns to the rewards of a just life. Since the gods know everything, they won't leave the just man unrewarded. Socrates tells a myth about a soldier named Er who is on the funeral pyre when he comes back to life.
It seems somewhat contradictory to use a story, a myth, as evidence, but the myth is presented as truth.
Er describes his experience in the afterlife. His soul and others traveled to a place where there were two chasms in the earth and two above in the sky. Judges sat in between the chasms. Just souls were sent to a chasm in the sky, to heaven, while the unjust went to a chasm in the earth. Souls from the two chasms were constantly moving. Those from the earth were dirty and worn, those from the sky, bright and shining. Er learned that souls in heaven are happy and content for a thousand years, while those in the earth suffer for a thousand years to atone for their crimes. Eventually the souls are summoned to the Fates who allow them to choose new lives. The souls are given a drink to make them forget their past lives. Er was about to choose a new life when he awoke and found himself on the pyre.
Socrates presents the myth of Er as proof not only of the immortality of the soul, but that the just man is rewarded in the afterlife.