This book develops and tests an argument to account for why and when one ethnic cleavage in an ethnically multi-dimensional society emerges as the axis of political competition and conflict instead of another. It builds its explanation around an account of the relative benefits that individuals receive from building or joining political coalitions constructed around different ethnic identities. I argue that the most beneficial identity will be the one that puts the person in a minimum winning coalition, and I show that, if everyone in society makes identity choices with this goal in mind, then a predictable ethnic cleavage will emerge as the basis of conflict in the political system.

The particular identities that individuals will find it most advantageous to choose will depend on the nature of the political system's ethnic cleavage structure. Understanding what the cleavage structure looks like is therefore a prerequisite for understanding the choices that political actors will make. To explain their choices, we will need to know two things about that structure. First, we will need to know the number of cleavage dimensions it contains. This will tell us the number of identities in people's repertoires and thus what the range of options is from which they are choosing. Second, we will need to know the number and relative sizes of the groups located on each cleavage dimension. This will help us (and the political actors) determine which identity it will be most useful to embrace.