Brann, Eva, "Why Justice? The Answer of the Republic," The Music of the Republic: Essays on Socrates' Conversations and Plato's Writings, Philadelphia: Paul Dry Books, 2004, 246-55.

Excerpt:

In literature as in life, justice is taken to be something good, and there are two questions about “good” that are hard to ask. The harder one is “Why is good better than bad?” When Stan leaps over the wall into Milton’s Paradise he utters to himself the words “Evil, be though my good,” perhaps the most disastrous utterable sentence imaginable; it is Thrasymachus’s argument that injustice is better than justice on a cosmic scale and raises the question how the bad can get the name good.

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