FOR nearly two decades now Michael Walzer has occupied a position shared by few other American political writers: He is, to revive the disused term, a public philosopher. Though many mediocre thinkers have claimed that title in the past, I use it in its highest sense and with the greatest admiration. At a time when political theory within the university has devolved into donnish chit-chat in the Oxbridge style, or “politics” in the Marxist sense, Walzer stands out. He is a highly literate man who taught political philosophy without pretending that he himself had anything novel to say about political metaphysics; he has been happy in his essays to float just above the contemporary.