Answer: a state that regulates every aspect of citizens’ lives in their best interests.
The Republic is a Socratic dialogue written by Plato around 380 BC. The work mostly concerns the topic of justice. It is one of the most influential works of philosophy and political theory.
In the dialogue, Socrates discusses several types of regimes, and concludes that the one ruled by philosopher kings is the best one. In this system, a central government would regulate every aspect of the citizens' lives in their best interests.