This afternoon I was listening to a podcast in which the Plato scholar Jacob Howland was being interviewed. At one point he brought up the ring myth from Plato's Republic. The basic idea is, as I got it, is that people are such that if any of us had an invisibility ring and hence could do whatever we wanted without being caught, we would commit numerous injustices. Although of course it wasn't mentioned in the podcast, it immediately brought to mind this principal doctrine as yet another answer to Plato.
At another point Howland mentioned that all-knowing gods were invented to solve this problem, and part of the rationale behind the totalitarian regime of the Republic is to create a society with no privacy in order to eliminate injustices committed in this way. Howland, to his credit, immediately pointed out the irony of that! He also pointed out that many totalitarians throughout history have referred to the Republic as a working manual. Further, the thinking was (and still is!) that if somebody is not afraid of, or does not believe in, all-knowing gods, then they will commit injustice.
This serves as yet another illustration of the stakes of the conflict between Epicurus and the Platonists. It's also an illustration of the optimism of Epicurus, although many see materialist philosophy as leading to nihilism and hopelessness!