During constructivism's formative period neorealism was the dominant discourse of international relations, thus much of constructivism's initial theoretical work challenged basic Neorealist assumptions. Neorealists are fundamentally causal structuralists, in that they hold that the majority of important content to international politics is explained by the structure of the international system, a position first advanced in Kenneth Waltz's "Man, the State, and War" and fully elucidated in his core text of Neorealism, "Theory of International Politics". Specifically, international politics is primarily determined by the fact that the international system is anarchic – it lacks any overarching authority, instead it is composed of units (states) which are formally equal – they are all sovereign over their own territory. Such anarchy, Neorealists argue, forces States to act in certain ways, specifically, they can rely on no-one but themselves for security (they have to self-help). The way in which anarchy forces them to act in such ways, to defend their own self-interest in terms of power, neorealists argue, explains most of international politics. Because of this, Neorealists tend to disregard explanations of international politics at the "unit" or "state" level. Kenneth Waltz attacked such a focus as being reductionist.