Summary: Book IX, 580d–end

Socrates has just provided us with one compelling reason to believe that justice is worthwhile: he has shown how much happier the just man is than the unjust. Now he provides us with a second argument for the conclusion that the just life is the most pleasant. There are three sorts of people in the world, goes the argument: truth-loving, honor-loving, and profit-loving. Each one of these people takes the greatest pleasure in whatever it is they most value and thinks that the best life is the life that involves the most of this pleasure. Yet among these, only one of them can be proved to be right. Only the philosopher is in a position to make this judgement, because only he has actually experienced all three pleasures. So we ought to believe the philosopher when he says that the pleasure of truth-seeking is the greatest pleasure. If the philosopher is right, the pleasure one gets from having a just soul (i.e., a soul aiming at fulfilling reason’s desires) is the best kind of pleasure. So, once again, we see that it does pay to be just.

The next argument also involves pleasures. Socrates argues that the pleasure of the philosopher is the only real pleasure. All other pleasures are actually relief from pain, not positive pleasure. Other pleasures are not real pleasures because other desires can never be completely satisfied. All we do is quench those yearnings tem-porarily, easing the pain of wanting. The philosophical desire can be completely fulfilled by grasping the Form of the Good.

Socrates now calculates that a king lives 729 times more pleasantly than a tyrant. This calculation is not supposed to be taken seriously, but is intended to emphasize that the just man is much happier than the unjust.

Finally, Socrates presents two refashioned portraits of the just and unjust man to replace the false portraits outlined in Book II. He asks us to envision that every human being with three animals inside of him: a multi-headed beast, a lion, and a human. If a man behaves unjustly, he tells us, then he is feeding the beast and the lion, making them strong, and starving and weakening the human being so that he gets dragged along wherever the others lead. He also fails to accustom the three parts to one another and leaves them as enemies. In the just person, the human has the most control. He takes care of the beast like a farm animal, feeding and domesticating the tame heads and preventing the savage ones from growing. He makes the lion his ally. The three parts are friends with each other. Socrates runs through various vices, such as licentiousness and cowardice, and shows how the three parts run amok to cause these vices.

Socrates declares that it is best for everyone to be ruled by divine reason, and while ideally such reason would be within oneself, the second best scenario is to have reason imposed from outside. This is the aim of having laws. The purpose of laws is not to harm people, as Thrasymachus claims, but to help them. Laws impose reason on those whose rational part is not strong enough to rule the soul.

Analysis: Book IX, 580d–end

Plato’s stated goal was to show that justice is worthwhile even in the absence of the rewards it might confer. In Book IX he argues that justice pays precisely because of such advantages. It will make for the most pleasurable life. If this is his argument, then he is failing to live up to his promises.