Full Idea
For Plato, the problem of making the ethical into a force was the problem of making society embody rational justification, and that problem could only have an authoritarian solution.
Gist of Idea
Plato found that he could only enforce rational moral justification by creating an authoritarian society
Source
comment on Plato (The Republic [c.371 BCE]) by Bernard Williams - Ethics and the Limits of Philosophy Ch. 2
Book Reference
Williams,Bernard: 'Ethics and the Limits of Philosophy' [Fontana 1985], p.27
A Reaction
Plato's citizens were largely illiterate. We can be more carrot and less stick.