Full Idea
The theory that our soul exists even before it enters the body surely stands or falls with the soul's possession of the ultimate standard of reality.
Gist of Idea
Whether the soul pre-exists our body depends on whether it contains the ultimate standard of reality
Source
Plato (Phaedo [c.374 BCE], 092d)
Book Reference
Plato: 'The Last Days of Socrates', ed/tr. Tredennick,Hugh [Penguin 1969], p.148