This chapter takes the philosopher Karl Leonhard Reinhold as a starting point to look at the ways in which critical philosophers sought to cast Kantianism as the heir to Protestantism. In his highly influential Letters on the Kantian Philosophy, Reinhold argues that the “first” Reformation of the sixteenth century was only a “preparation” for the current attempts to purify morality through philosophy. Situated in the context of Friedrich Heinrich Jacobi’s accusation that contemporary philosophy led to atheism (the so-called pantheism controversy or Spinozastreit) it traces Reinhold’s evolution from a proponent of the Catholic Enlightenment to an energetic advocate for Kantian philosophy at the University of Jena. Concluding briefly with Johann Gottlieb Fichte, the chapter shows how the new language of Protestantism discussed in the previous chapters proved fruitful for advocates of the new philosophy.