Having described his ideal state, and the series of elaborate lies it is based on, Plato/Socrates concludes that the only fit ruler would be a philosopher king. And what is the central qualification of the PK?
SOCRATES: Then let’s begin our dialogue by recalling the starting point of our description of the nature that someone must have if he is to become a fine and good person. First of all, if you remember, he was led by truth,133 [490a] and he had to follow it wholeheartedly and unequivocally, on pain of being a lying imposter with no share at all in true philosophy.
Readings in Ancient Greek Philosophy: From Thales to Aristotle (p. 337). Hackett Publishing Company, Inc.. Kindle Edition.