In recent years, constructivist thinking about global politics has brought a breath of fresh air to international relations. By exploring questions of identity and interest, constructivist scholars have articulated an important corrective to the methodological individualism and materialism that have come to dominate much of ir. As the books under review indicate, constructivism has also succeeded in demonstrating its empirical value--documenting a new and important causal role for norms and social structure in global politics. Theoretically, however, the approach remains underspecified. In particular, constructivists typically fail to explain the origins of such structures, how they change over time, how their effects vary cross nationally, or the mechanisms through which they constitute states and individuals. Missing is the substantive theory and attention to agency that will provide answers to such puzzles, as well as ensure the development of a productive research program.