Final answer:
In Virgil's 'Aeneid' Book 6, Aeneas and his fleet journey to the underworld to meet Anchises, who enlightens Aeneas about Stoic cosmology and the Orphic cycle of soul rebirth.
Step-by-step explanation:
In Book 6 of Virgil's epic poem Aeneid, Aeneas and his fleet make their way to the underworld, where they encounter various spirits and ultimately Aeneas meets his father, Anchises. Anchises is found reviewing the souls of his descendants who are predestined to reach the 'upper light'.
He then explains to Aeneas a Stoic view of cosmology, which includes the cycle of death and rebirth where souls drink from the Lethe to forget their past lives before being reincarnated. Significant influence from Orphic traditions and other sources like Plato's conception of the soul in the body is evident here. Virgil utilizes these sources to create a rich tapestry of the afterlife that reflects Roman beliefs and incorporates existing Greek and Orphic elements.