What is arguably the most contested aspect of twenty-first century politics is identity politics. It is the forward edge of the battle era in cultural wars over sex, gender, marriage, justice, welfare, race, ethnicity, and immigration. But what is identity and how did it become the thing shaping so much of our politics?

We might say that that identity is the perceived homogeneity between a person and a group of persons – whether it is ethnic, racial, national, religious, cultural, gender-based, or sexual orientation – which enables a person to regard themselves as part of that group.