EACH YEAR, I BEGIN my Marx courses at the London School of Economics by telling my students that many people think of socialism as a theory of material relations, class struggle, or economic justice but that, in reality, something more fundamental animates it. Socialism, I tell them, is above all a theory of human freedom, of how to think about progress in history, of how we adapt to circumstances but also try to rise above them. Freedom is not sacrificed only when others tell us what to say, where to go, how to behave. A society that claims to enable people to realize their potential but fails to change the structures that prevent everyone from flourishing is also oppressive. And yet, despite all the constraints, we never lose our inner freedom: the freedom to do what is right.