Despite its weaknesses, Marxism contributes to the theory of international relations in at least four respects. First, historical materialism with its emphasis on production, property relations and class is an important counter-weight to realist theories which assume that the struggle for power and security determines the structure of world politics. This leads to two further points which are that Marxism has long been centrally concerned with capitalist globalization and international inequalities and that, for Marxism, the global spread of capitalism is the backdrop to the development of modern societies and the organization of their international relations. A fourth theme, which first appeared in Marx’s critique of liberal political economy, is that explanations of the social world are never as objective and innocent as they may seem. Applied to international politics, the argument is that the analysis of basic and unchanging realities can all too easily ignore relations of power and inequality not between states but between individuals. Dominant strands of Marxist thought have taken the view that one of the main functions of scholarship is to understand the principal forms of domination and to imagine a world order which is committed to reducing material inequalities. This critical orientation to world politics can no longer be simply ‘Marxist’ in the largely superseded sense of using the paradigm of production to analyse class inequalities. But it can nevertheless remain true to the ‘spirit of Marxism’ by combining the empirical analysis of the dominant forms of power and inequality with a moral vision of a more just world order. This critical approach can extend beyond the analy- sis of capitalist globalization and rising international inequalities to the ways in which states conduct national security politics. One of the failings of Marxism as a source of critical international theory is its ingrained tendency to focus on the former at the expense of the latter field of inquiry. Later chapters discuss whether other strands of critical international theory have succeeded in overcoming this limitation.