While I have you in pedagogical mode - would you say that the big difference between physicalist and Marxian materialism is that the former's defining premise holds that there is only matter and its motions. In the latter, matter is conceived as always already in relationship with all other relations, and it is therefore the (logically prior) realm of relationships that constitutes the basis of the 'materialist conception of history'.
I remember Tsuru once called Marx the 'institutionalist par excellence', and I'm under the impression that it was precisely this point he was making. On this account, political economy is the study of relationships of power in society, and international political economy, of power as it constitutes nation states and the relations between them. It seems to follow, then, that 'naive realism' in the field of international relations is open to some Marxian critiques:
1) the nation state is accorded the status of basic unit of analysis (the theoretical problem presented by the pre-Westphalian world is ignored, for a start) - when the relationship between the relations that constitute the nation state and those between nation states should be held as logically prior;
2) the ensuing model is an exact replica of the individualism that underpins economics; ie. the nation state as natural, eternal, rational, acquisitive and autonomous sovereign individual competing for scarce resources;
3) it implicitly confines resolution of problems to do with depletion and despoliation to contests up to and inevitably including war, for as the costs to the nation state of scarcity rises, so must the price it will pay to acquire resource security: war is international politics in its essence, and there are only absolute victors and absolute losers right up to the moment there is only one nation state left;
4) the nation state prevents collectively rational responses to crises, yet it can not wither away;
5) Realism gives us no options in the struggle to end terrorism other than (a) make the price of being associated with terrorists too high to pay for every nation state, (b) to employ whatever means to gain control over that nation state, or (c) to bring to an end that nation state. War is implicit in all three;
6) Realism does not explain and can not resolve the problem of terrorism, for the relationship between terrorism and the nation state is assumed, and assumed to be one of identity - hence the discursive contortions we see, whereby the enemy is ObL, which must be identified with Taliban if a war is to be be mounted, but which liberal values may not allow to be identified with Afghan, who, in the event s/he is killed in that war, must be recorded as a victim of the Taliban, because the only other thinkable culprit would be the USA. ObL, who is not at identity with Taliban at all, disappears from the story - and the idea of two elites, killing tens of thousands of helpless innocents in a contest in which neither innocent cohort had any stake, is completely effaced.
Or not?
Cheers, Rob.