If there are vague propositions it is natural to wonder what role they play in thought. A natural picture, given a linguistic theory of vagueness, is that one only learns a vague proposition via a public language sentence that expresses it (e.g. by hearing someone reliable asserting the sentence). This chapter argues that there are many ways to obtain vague evidence that do not involve language. It focuses on ‘inexact’ evidence acquired through imperfect perceptual faculties, and argues that the effect of inexact evidence on our credences is similar to the effect of conditioning on a vague proposition, and cannot easily be simulated by conditioning on any precise proposition. The chapter introduces the notion of an evidential role—a profile of the effects a certain piece of inexact evidence can have on your credences—and outlines the central principle of vague propositions: the Principle of Plenitude. This principle states that there is a vague proposition occupying every evidential role.