This is the first in an occasional series of blogs on social boundaries and identity. I’m interested in the topic for obvious reasons. Social boundaries and identities, at least in some forms (and that is the rub!) have been argued to affect generalized trust and/or prejudice, governance and cooperation, and development outcomes. They may also be relevant to certain recent political developments. Here at the World Bank, the Mind, Behavior, and Development Unit (eMBeD) is involved in projects that aim to support social cohesion.