Does the eighteenth-century Spinozism debate, in which Jacobi popularized the term “nihilism,” illuminate Nietzsche’s conceptions of nihilism and genealogy? Frederick Beiser interprets Jacobian nihilism as radicalized Cartesian skepticism, according to which even the subject of ideas is unknowable. Bernard Reginster distinguishes two senses of Nietzschean nihilism: a metaethical antirealism about our highest values and an ethical despair arising from the sense that our highest values are unrealizable. If both are correct, then juxtaposition is unilluminating. I argue that Jacobi and Nietzsche understand nihilism as a disruption of the formation of the subject capable of epistemic or ethical agency, operating in the dimension that Stanley Cavell calls moral perfectionism. Jacobi’s alternative to nihilism is lived historicity. The young Nietzsche realizes that critical historiography undermines this alternative and celebrates the annihilation of personal subjecthood in his inaugural lecture. In the Genealogy, Nietzsche seeks to develop a historiography empowering his readers to avoid nihilism by actively forming personal subjects. Genealogy’s effectiveness does not require truthfulness.