This article invokes a combination of analytical and normative arguments that highlight the leading role of practices in explaining the expansion of security communities. The analytical argument is that collective meanings, on which peaceful change is based, cognitively evolve - i.e. they are established in individuals' expectations and dispositions and they are institutionalized in practice - because of communities of practice. By that we mean like-minded groups of practitioners who are bound, both informally and contextually, by a shared interest in learning and applying a common practice. The normative argument is that security communities rest in part on the sharing of rational and moral expectations and dispositions of self-restraint. This thesis is illustrated by the example of the successful expansion of security-community identities from a core of North Atlantic Treaty Organization ( NATO) states to Central and Eastern European countries during the 1990s, which was facilitated by a 'cooperative-security' community of practice that, emerging from the Helsinki Process, endowed NATO with the practices necessary for the spread of self-restraint.
