I propose a theory aimed at advancing scholarly research in social entrepreneurship. By highlighting the key trade-off between value creation and value capture and explaining when situations of simultaneous market and government failure may arise, I suggest that social entrepreneurship is the pursuit of sustainable solutions to neglected problems with positive externalities. I further discuss the situations in which problems with externalities are likely to be neglected and derive the central goal and logic of action of social entrepreneurs, in contrast (...) to commercial entrepreneurs. Overall, this article provides a conceptual framework that allows understanding the growing phenomena of social entrepreneurship and its role in the functioning of modern society. (shrink)