In post-Reformation England, intense pressures on belief produced sophisticated theorizations of habitual assent and of habit itself. These have been largely overlooked by scholarship on the Reformation because of its fixation on doctrine and confessional identity—the very obsession this scholarship imputes to its subjects. Implicit faith emerges again and again in these theorizations not just as a menace to, but also a condition of, strong belief. Nor is this a local phenomenon: examples are drawn from a wide doctrinal and chronological range (William Perkins, Godfrey Goodman, John Milton, John Wesley). There is evidence of a parallel development in scientific circles, as practitioners like Robert Boyle reflected on the necessary role of implicit faith in the collective production of knowledge, a project to which the ideal image of the self-determining individual, inwardly persuaded by testimony, was not finally adequate. Recent critiques of the Reformation by such writers as Brad Gregory and Jennifer Herdt have thus underestimated the extent to which their critiques were immanently produced within Protestantism itself.