If justice is the most profound responsibility of public life, it is also the one we are least suited to fulfill. It’s no mystery why this should be. We’re human. Our byways are complicated. The institutions of law are infected with the same shortcomings—greed, dishonesty, weakness, indifference, anger—that give rise to injustice in the first place. On the everyday working level, criminal justice is like chemotherapy. We throw our little poisons at big ones.

This may be the most entertaining irony of human affairs. (Literally entertaining—we get any number of our movies, books and TV shows out of it.) In such an ancient predicament, can anything new ever happen? Sure it can. Proposing to tell God himself that he has no right to treat you unjustly was once a big advance (see Book of Job). So were trial by jury and the right to remain silent. So were fingerprinting and dna evidence. So was the electric chair.

We want to be good. We want to be bad. Between these sides of ourselves, we construct the wall of the state, which is porous, since it’s made of ourselves (see Bill Clinton). Assuming that you’re in favor of justice, anything that makes it stronger is good news, right? We have good news.