Knowledge and Power

While he may or may not admit the city is impossible to achieve, Socrates' point is that acquiring Perfect Knowledge is the key to success. Knowledge is one of the abstract "realities" in this world, and by attaining perfect knowledge, Philosophers can rule the city without making any mistakes. This brought two scriptures to mind, 

Psalm 127:1

Unless the Lord builds the house, they labor in vain who build it; Unless the Lord guards the city, the watchman keeps awake in vain. 

1 Corinthians 1:24-25 "To those who are the called, both Jews and Greeks, Christ the power of God and the wisdom of God, because the foolishness of God is wiser than men, and the weakness of God is stronger than men."

We can make all kinds of assumptions and observations about human behavior, but until we realize that the real problem is our sinful nature, and the only solution is God's grace, it won't matter what real justice is or how we get it.