Since the early 1950s, there has been lingering terminological and conceptual confusion in evolutionary biology regarding the definition and mechanism of the Baldwin effect (BE) and genetic assimilation (GA). This paper aims at clearing it up by proposing a distinction of the conceptions of the phenotypic effects of genetic mutations in BE and GA, relying on a classical distinction in metaphysics between two main kinds of properties: "extrinsic" and "intrinsic". I argue that in its traditional understanding, BE implies that mutations' effects on the phenotype are dispositional (i.e. intrinsic) properties, whereas GA needs them to be systemic (i.e. extrinsic) properties.