In modern continental thought, natural science is widely portrayed as an exclusively instrumental mode of reason. The breadth of this consensus has partly preempted the question of how it came to persuade. The process of persuasion, as it played out in Germany, can be explored by reconstructing the intellectual exchanges among three twentieth-century theorists of science, Heidegger, Habermas, and Werner Heisenberg. Taking an iconic Heisenberg as a kind of limiting case of “the scientist,” Heidegger and Habermas each found themselves driven to place new constraints on their previously more capacious assessments of science, especially its capacity to reflect on its method. Tracing how that happened, through archival and historical contextualization and close readings of their texts, lets us make visible Heidegger and Habermas’s intellectual affinities and argumentative parallels, which derived not only from their shared grounding in earlier reactions against positivism, but also from confrontation with contemporary events. The latter included, for Heidegger, the rise of a technically powerful science exemplified by nuclear physics, and for Habermas, post-World War II controversies over science, technology, and their socially critical possibilities.