An opposition of idealism and materialism is one of the two ­oppositions often used in definitions of constructivism, particularly in the United States. But this simple dichotomization of these two concepts is misleading, in a variety of ways. It grossly simplifies what is in fact a more complicated relationship between the two concepts, in the process both creating a straw man of realism and confusing core definitional issues of constructivism. It confuses issues of ontology (the materiality of things) with issues of epistemology (whether or not we can study politics in the abstract). And it obscures relationships between both constructivism and realism on the one hand and various other approaches to the study of international relations on the other.

Idealism is itself a tricky term. Wendt distinguishes between idealism (the -ism of ideas) as a social theory of politics and Idealism (the -ism of ideals, which he capitalizes) as a theory of IR. The first idealism refers to social theory that looks at the importance of ideas, whereas the second refers to a theory of IR based on ideals rather than on realism. It is in the former manner, as the -ism of ideas, that idealism is used by Wendt and others as a definitional component of constructivism, and it is with this definition that the term is used in this chapter. The other usage, idealism as the -ism of ideals, is discussed in Chapters 5 and 8.