According to an influential view, asserting a proposition involves undertaking some “commitment” to the truth of that proposition. But accounts of what it is for someone to be committed to the truth of a proposition are often vague or imprecise, and are rarely put to work to define assertion. This article aims to fill this gap. It offers a precise characterisation of assertoric commitment, and applies it to define assertion. On the proposed view, acquiring commitment is not sufficient for asserting: (...) To assert, commitment must be acquired by explicitly presenting a proposition as true. (shrink)