Causative and applicative morphemes have been central in work on the morphosyntax of argument structure. However, several genetically unrelated languages use a single, syncretic form for both functions, which complicates the traditional view that a causative adds a new subject and an applicative adds a new object. In this paper, I propose an analysis of a morphological syncretism found in the Bantu language Kinyarwanda where the morphological causative and instrumental applicative are both realized by the morpheme –ish. I argue for Kinyarwanda that both causation and the introduction of an instrument are analyzable as two outgrowths of the same semantic notion of introducing a new link into the causal chain described by the verb. The different causative and instrumental readings derive from underspecification of the position of the new link in the causal chain, although its placement is restricted via general constraints on possible event types as well as constraints on verb meaning and argument realization. This analysis provides an explanation for the presence of the causative–instrumental syncretism as well as provides insight into the interface between verb meaning and valency-changing morphology.