of Power Politics" published in International Organization laid the theoretical groundwork for challenging what he considered to be a flaw shared by both neorealists and neoliberal institutionalists, namely, a commitment to a (crude) form of materialism. By attempting to show that even such a core realist concept as "power politics" is socially constructed—that is, not given by nature and hence, capable of being transformed by human practice—Wendt opened the way for a generation of international relations scholars to pursue work in a wide range of issues from a constructivist perspective. Wendt further developed these ideas in his central work, Social Theory of International Politics (1999). Following up on Wendt, Martha Finnemore offered the first "sustained, systematic empirical argument in support of the constructivist claim that international normative structures matter in world politics" in her 1996 book National Interests in International Society. There are several strands of constructivism. On the one hand, there are "conventional" constructivist scholars such as Kathryn Sikkink, Peter Katzenstein, Elizabeth Kier, Martha Finnemore, and Alexander Wendt, who use widely accepted methodologies and epistemologies, and whose work has been widely accepted within the mainstream IR community and generated vibrant scholarly discussions among realists, liberals, and constructivists. These scholars hold that research oriented around causal explanations and constitutive explanations is appropriate. Wendt refers to this form of constructivism as "thin" constructivism. On the other hand, there are "critical" radical constructivists who take discourse and linguistics more seriously, and adopt non-positivist methodologies and epistemologies. Both thin and thick versions of constructivism agree that neorealism and neoliberalism pay insufficient attention to social construction in world politics. There is yet another strong strand of critical constructivism that takes conventional constructivists to task for systematically downplaying or omitting class factors. Theory Constructivism primarily seeks to demonstrate how core aspects of international relations are, contrary to the assumptions of neorealism and neoliberalism, socially constructed. This means that they are given their form by ongoing processes of social practice and interaction. Alexander Wendt calls two increasingly accepted basic tenets of constructivism "that the structures of human association are determined primarily by shared ideas rather than material forces, and that the identities and interests of purposive actors are constructed by these shared ideas rather than given by nature." This does not mean that constructivists believe that international politics is "ideas all the way down", but rather that international politics is characterized both by material factors and