The major theme of Kwame Anthony Appiah's book The Ethics of Identity could be paraphrased as, "your identity isn't yours." What I mean by that is, you can believe whatever you want about yourself, but what others believe about you is just as important. No one exists in total isolation, and the relationships you form with people, institutions, and your environment are what make you, just as much as your own thoughts do.

The sub-themes of the book, like the meaning of individual liberty, the paucity of culture, and the need to really understand yourself all appear in one chapter or another. They're held together by the notion that your identity is a two-way street. Social theorists, especially left-wing ones, call this a dialectic. Your beliefs influence external actors and factors, and those in turn influence your beliefs. Out of this process comes our identity.

A big realization, which follows once you accept the premise that your identity isn't totally under your control, is that your identity not static, either. If the world is at least in part responsible for who you are, and the world is always changing, that means your identity is always changing, too. Really, it's a struggle. If I say I'm a conservative person, but I relate to others in a way they recognize as liberal and inclusive, I'm still a liberal? And what if the company I keep changes, even though my ideas don't change, and my new interlocutors say I'm a pretty mean person? That change affects my identity because it affects the way the world and I get along, even though the changes aren't under my control.

These themes can all be traced back to the "nature vs. nurture" arguments of the early Enlightenment. In fact, Appiah spends his whole first chapter discussing the life and work of John Stuart Mill, the nineteenth-century philosopher who is one of the most celebrated intellectual descendants of the Age of Reason. "What makes me what I am?" is a question Appiah comes back to often in the book. His chapters build the answer, from individual liberty to personal autonomy, from personal responsibility to community relationships, from self-reflection to self-realization, and finally to the realization that, like it or not, we're all part of a great big world.