The question of Martin Luther's influence on Stanley Cavell has been almost entirely neglected in the extensive scholarly literature on Cavell. Yet, Luther's name appears prominently and repeatedly in Cavell's initial discussions of his central concepts of acknowledgment and the truth of skepticism. Though the former is often taken to be an essentially interpersonal matter, I argue that it concerns first and foremost that aspect of the world Kant names the Ding an sich, and that Cavell's understanding of this follows Luther's conception of our proper relation to God. On this basis, I then argue that Luther's “baptismal life” contains most of the essential elements of Cavell's Romanticism and what he will later term Emersonian Perfectionism. This perfectionism is in effect an “alternative secularization” of Luther's Reformation. As with Kierkegaard, on whom Cavell also draws heavily, though Luther appears less and less in Cavell's work after The Claim of Reason, his initial influence on Cavell's central ideas is decisive.