Transnational activist networks alter world politics by promoting the emer­gence and diffusion of new international norms. Why do these networks take up some worthy causes but not others? Charli Carpenter tackles this question and offers convincing answers to it in “Lost” Causes. Carpenter shows that gatekeeper organizations—those that are most connected to others and that bridge diverse subnetworks—vet emerging issues. “Agenda vetting” shapes the issue agenda, that is, the set of problems to which governments, international organizations, and other actors pay attention. Carpenter’s central argument is that agenda vetting involves not just the power of resources or the power of ideas but also the power of network position. “Lost” Causes is a major advance in research on transnational activist networks and international norm change.

The theory advanced in “Lost” Causes emphasizes selection: issues reach, and rise on, the agenda of advocacy networks when they are taken up by organizations that are network hubs. Advocacy elites—who occupy the net­work’s central nodes—decide which new issues to add to their organizations’ list of causes. The preferences of these elites are shaped by “perceptions of intranetwork relationships” (p.