The take away of MSW is pretty simple: any explanation of foreign policy decisions must always start with an assessment of the international environment (i.e., the balance of power among sovereign states). The international environment sets the opportunities and constraints of action or its "permissive cause." The "proximate" causes for action stem from other factors, either as the result of the preferences of individuals in positions of authority or from peculiarities of particular state actors (their politics, their political cultures, etc.).Yes, okay, I get that--and I can see how it needed (re)stating in the context of the times, even if, perhaps,it was in part a restatement of Machiavelli (or even better, Rousseau). States function in an environment of anarchy. We cannot "just get along;" our problems will not just go away if we understand each other better. States do use power--but not least to insure their own survival, The kind of power they use (the way they use it) is in large measure a function of their situation in the anarchic scramble.
This is perhaps not as anodyne as it may sound--important statements rarely are--although I suspect that not many people would quarrel with it today. What is perhaps more interesting from the standpoint of history is the centrality it gives to the notion of the "state." Granted, I don't suppose we have a better building block today, but from what little I know, I gather the dominant theme of so much of international relations over the past generation or so has been the erosion of the estate and its replacement by--oh, boy; by NGOs, by Nonprofits, by international organizations, by international bankers, by mafias, by who-knows-what competitor to the traditional sovereign.
This can't be a fatal criticism, of course. Any serious thinker is answering his own questions, not ours, and any serious political thinker is writing about his politics, not ours-I like the way Waltz situates Machiavelli in the particular circumstances of the Italy of his time. If it is true for Machiavelli--or Thucydides, or Hobbes--then there is no reason to suppose it is any less true of Waltz. Must have been an interesting experience, to write a masterpiece at the beginning of a career, and to watch it mature into a truism, and then to become old hat.