Full Idea
Once gods and fate and social expectation were no longer there, Plato felt it necessary to discover ethics inside human nature, not just as ethical knowledge (Socrates' view), but in the structure of the soul.
Gist of Idea
As religion and convention collapsed, Plato sought morals not just in knowledge, but in the soul
Source
comment on Plato (works [c.375 BCE]) by Bernard Williams - Shame and Necessity II - p.43
Book Reference
Williams,Bernard: 'Shame and Necessity' [California 1994], p.43
A Reaction
anti Charles Taylor