In a wooded valley through which the river Lethe flowed, Aeneas saw innumerable souls: they looked like bees in a meadow on a still summer‘s day. Anchises explained that they were souls who were waiting to return to earth and live a second time: they drink the water of Lethe to forget everything in their previous lives.
Among them are the not-yet-born descendants of Anchises and Aeneas.
Anchises tries to explain what it all means: the Universe is controlled by a mind. This mind or spiritus is in everything, and in all creatures, including man. Unfortunately, through prolonged contact with the body (which has sinned and committed crimes), in most men this spirit becomes tainted and corrupted. It needs therefore to be cleaned up before it can be re-issued to another body. Different sins are cleansed from the soul in different ways - we all find the punishment we deserve. Once purified, the souls remain in Elysium for a thousand years, after which they await the summons to rebirth.