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 paper aims to fill this gap. It offers a precise characterisation of assertoric commitment, and shows how it can be applied 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)