Discussions of modality (e.g. Bybee, Perkins & Pagliuca, 1994; Coates, 1983; Lyons, 1977; Palmer, 1986; Traugott, 1989) typically center around two issues: deonticity vs. epistemicity, and degree of subjectivity. Using diachronic evidence from the quasi-modal ought to, this paper argues for the need to recognize a third, crosscutting these two: narrow vs. wide scope. We argue that the epistemic use of ought to developed out of a wide-scope deontic construction, in which the modal was used with deontic meaning, but with propositional scope (contra Bybee, 1988). Rather than attributing an obligation to the subject (i.e. having narrow scope), the modal in this construction makes an assertion about the proposition as a whole, like an epistemic. However, such ought to constructions are found some four hundred years before the first epistemic examples, and thus can be shown to be distinct from epistemic uses (contra Gamon, 1994).