The Waltzian Paradigm, developed by its namesake Kenneth Waltz, outlines a way to theorize about international politics that is characterized by the assumption that theories of domestic politics are not useful for understanding international politics. Indeed, it must be considered as an entirely separate category with entirely separate theories. The paradigm is significant because it gave was used by many other theorist besides Kenneth Waltz himself.
All theories of international politics, which make use of the Waltzian paradigm, share certain common traits such as anarchy as a key starting point, system-level influences on state behavior, and convergent evolution.
Anarchy, or the lack of a sovereign in international relations, as a key starting point means there is an intrinsic lack of order in IP. As such a states ability to maximize their interests depends on their ability to help themselves because with no sovereign and a state level state of nature, states can do what they wish. A sort of expression of the idea that the strong do what they want and the weak suffer what they must.
In addition, the Waltzian paradigm focuses on systemic-level influences on state-behavior out of a belief that lesser factors such as leader, regime type, and economic development matter much less than the total pressure exerted by the international system as a whole.
Finally, those theorists who use the Waltzian paradigm assume convergent evolution follows. This is an adaptation of the biology term isomorphism, or the tendency of organisms with different ancestries to evolve similar responses to similar environmental pressures. If a species or in this case a state does not follow this plan they will go extinct. So in the minds of these theorists all states will respond the same or suffer making opening the black boxes unnecessary.