The legal doctrine that assign blame for international crimes are numerous, unclear, ever-changing and often conceptually problematic. In this Essay, I question the prudence of retaining the radical doctrinal heterogeneity that, in large part, produces this state of disarray. Instead of tolerating different standards of participation across customary international law, the ICC statute and national systems of criminal law, I argue for a universal concept of participation that would apply whenever an international crime is charged, regardless of the jurisdiction hearing the case. Although I have argued elsewhere that a unitary theory of perpetration should serve this role, I here attempt to remain agnostic about the content of the universal system for which I advocate. In so doing, I isolate the question of universality from the theory of responsibility that would fill it, querying why so much energy is invested in generating treaties to harmonize definitions of international crimes, when no comparable initiative exists for the modes of participation these crimes couple with. I conclude this call for a universal notion of participation in atrocity by suggesting that the current disarray in this domain is more a challenge for academics and states than litigators and judges.