Plato's Republic

At the beginning of the Republic the sophist Thrasymachus argued that might makes right, that what we call justice or morality or virtue or ethics is really nothing more than what those in power want us to value.   The mighty in effect dictate what is considered right, and there is no other meaning to 'right' than this.  (So Thrasymachus is a skeptic, not an egoist like Callicles.)  Being 'good' or 'nice' is a recipe for losing, for doing what is in the interest of the powerful, not of yourself.

Glaucon then challenges Socrates (who here speaks for Plato) to prove that virtue really is its own reward, that it is in one's own self-interest to be good or just or ethical.  According to Glaucon most people believe that moral goodness is really a kind of necessary evil.  Ideally we would do what we want and get away with it, but in reality this causes problems so we compromise and agree to follow certain rules.  Doing the right thing makes society as a whole happier, keeps individuals out of trouble, can get you a good reputation, and keeps you from going to Hell when you die.  So it is worth it, but, most people think, it is not the best one can imagine.  That would be having the power to do wrong and get away with it.

Socrates/Plato argues that being good or just is not a matter of following certain rules but of having a certain kind of character.  A virtuous character is one whose parts are in the right balance.  These parts, and this balance, are easier to discern if we imagine a society.  Any society needs wise rulers, loyal and brave armed services (including police), and law-abiding productive workers.  A just society is one with all these parts working together properly.   Similarly, a just individual is one with well-controlled appetites ruled by the wise, rational part of his/her soul, supported by a courageous spirit.  This individual is virtuous because he or she has the four cardinal virtues of wisdom, temperance, courage, and justice.

Is it in one's self-interest to be virtuous in this way?   Yes, because these virtues are things we need in order to be happy.  Without wisdom we will do stupid things that we are likely to regret.  Without courage we will chicken out of things we want to do.  Without temperance we will go too far and end up broke or sick or both.  Without justice we will not have the right balance.   For instance, we might be brave when it would be wiser to back down, or show misplaced loyalty when a true friend would not let his friend behave dishonorably.   So Thrasymachus and Glaucon are both wrong, Plato thinks.