Abstract
The article proposes an approach to the types of functioning and mechanisms of change intervening in the rise of the discourse marker comme de raison in French, associated with evidentiality. The diachronic analysis provides the opportunity to study the relationship between comme de raison and the meanings of raison, but also the type of structure at the origin of the discourse marker. The status of the construction will be questioned, which is intertwined with the discussion about the mechanism of change (lexicalization, grammaticalization / pragmaticalization, cooptation). The semantic evolution could be described as follows: from « what is normal, right to do, what should be done » to « what is normal, right to say, what should be said », since this could be inferred from a previous sentence or a more general context.