Vagueness in language and cognition has traditionally been interpreted in semantic or epistemic terms. Specifically, on the standard picture of vagueness, it is suggested that considerations of agency or rationality, broadly conceived, can be left out of the equation. Likewise, theories of rationality in choice behaviour traditionally abstract from the potential vagueness of notions that are fundamental to the theory of rational decision-making, such as credence or preference. It is in this regard fair to say that theories of vagueness and theories of rationality tend to be premised on the idea that they...