On the titlepage of his collection of sermons, The Happinesse of the Church (1618), Thomas Adams styled himself “preacher” at St. Gregory’s, London. The term could indicate puritan leanings, and in the nineteenth century Robert Southey went so far as to call Adams “the prose Shakespeare of puritan theologians… scarcely inferior to Fuller in wit or to Taylor in fancy.” Adams often used the word “puritan” pejoratively. Historians, however, have classified as puritans people who rejected the term for themselves, just as political analysts-sometimes justly-classify as “liberals” or “conservatives” politicians who cavil at these terms. The problem, as always, is one of definition, and Adams affords an excellent opportunity to test the adequacy of our definitions. Like “humanist” or “republican,” “puritan” is one of those terms that have come to have a meaning that transcends the circumstances in which they originated. I argue that Adams was not a puritan; he was instead a mainstream Calvinist episcopalian of the kind so convincingly described by Patrick Collinson in his Ford lectures. Nevertheless, an attempt to place Adams in the spectrum of religious opinion has a value beyond merely getting one individual situated. Scholars have contradicted each other in their placing of Adams, and this analysis, by getting him right, will throw light on our understanding of the varieties of Calvinism in early Stuart England.