While contingency and negation are relatively well-established notions in the theoretical analysis of international relations, their practical implications remain under-conceptualised. In order to discuss the question of how to act under conditions of contingency and negation, this article, in a first step, triangulates both with Aristotelian noesis. Such triangulation suggests that the consequences of political action cannot be predicted and always have inadvertent consequences due to the contingent and historically and intellectually negated and refutable (even self-refutable) character of politics. It therefore appears as irresponsible to enact policies with interminable consequences. Rather, responsible political action — which is responsible precisely as, and only if, it accounts for contingency and negation — must hence act only in such a way that its consequences are reversible. In a second step, policy theory is critically reviewed in light of reversibility and its underlying philosophical principles, trying to bridge political philosophy and policy studies for a mutually enriched analysis of politics. Such a bridging exercise not only brings enhanced normative reflection into policy studies, but also, in reverse, hints at the crucial aspect of the non-linear unfolding of action consequences, which is, in addition to questions for a future research agenda, discussed in the concluding section. These discussions are understood as a twofold, yet interlinked, contribution: first, to develop a concept of reversibility as a practical response to the philosophical notions of contingency and negation; and, second, to bridge two different paradigms, encouraging the synergy of scholarly expertise for the management of contemporary international and global problems.