The impact of the outside world must pass through an intellectual medium; and the only question is how strong is its refraction, to what extent it possesses independent vigor and can exert a counterweight…. We can – indeed, must – stress that in the life of peoples external events and conditions exercise a decisive influence upon the internal constitution…. There is a constant collaboration of the inner and outer world.

When you open the door, some flies inevitably come in.

The international system, be it in an economic or politico-military form, is underdetermining. The environment may exert strong pulls but short of actual occupation, some leeway in the response to that environment remains. A country can face up to the competition or it can fail. Frequently more than one way to be successful exists. A purely international system argument relies on functional necessity to explain domestic outcomes; this is unsatisfactory, because functional requisites may not be fulfilled. Some variance in response to external environment is possible. The explanation of choice among the possibilities therefore requires some examination of domestic politics.