Letters 88.34

There are countless questions concerning the soul alone: whence it comes, what is its nature, when it begins to exist, and how long it exists; whether it passes from one place to another and changes its habitation, being transferred successively from one animal shape to another, or whether it is a slave but once, roaming the universe after it is set free; whether it is corporeal or not; what will become of it when it ceases to use us as its medium; how it will employ its freedom when it has escaped from this present prison; whether it will forget all its past, and at that moment begin to know itself when, released from the body, it has withdrawn to the skies.

Seneca, Letters to Lucilius 88.34, translated by Richard Mott Gummere