Structural realism, classical realism and human nature

Kenneth Waltz's Theory of International Politics is a modern classic, and deserves to be read the way classic texts ought to be read, i.e. in context and in its own terms. Recovering the context in this case is difficult because of the changes in the discourse since 1979, but one difference between the contemporary and the current reception of the text does seem clear — Waltzian structural realism (or neorealism) is now, but was not then, seen as breaking with the traditions of classical realism. How is this discontinuity to be understood? Part of the answer lies in the rhetoric employed by participants in this debate, but, more substantively, there is a genuine disagreement between neorealism and classical realism over the role played by human nature in international relations. Waltzian neorealism appears, contrary to the tradition, to reject any major role for human nature, describing theories that emphasise this notion as `reductionist'; however, on closer examination, the picture is less clear-cut. Waltz's account of human nature can be related quite closely to the major strands in the realist genealogy, but at a tangent to them. Interestingly, and perhaps unexpectedly, it is also compatible with at least some of the findings of contemporary evolutionary psychology