A case for a certainty norm of assertion

According to the widely endorsed Knowledge Account of Assertion, the epistemic requirements on assertion are captured by the Knowledge Norm of Assertion, which requires speakers only to assert what they know. This paper proposes that in addition to the Knowledge Norm there is also an Epistemic Propositional Certainty Norm of Assertion, which enjoins speakers only to assert p if they believe that p on the basis of evidence which makes p an epistemic propositional certainty. The paper explains how this propositional certainty norm accounts for a range of data related to the practice of assertion and defends the norm against general objections to certainty norms of assertion put forward by Duncan Pritchard, John Turri, and Timothy Williamson, by drawing on linguistic theories about epistemic modals and gradable predicate semantics. Together these considerations show that the prospects of a certainty account of assertion are much more promising than is usually assumed.