It is a common view that Descartes' causal principle is to be understood in light of a similarity condition that accounts for how finite causes contribute to an explanation of their effects. This paper challenges this common view and offers a sui generis reading of Descartes' views on causation that has also the advantage of solving the two exegetical issues of whether Descartes thought of the body-to-mind relation in occasionalist or causal terms and of whether Descartes regarded sensory ideas innate (...) or caused by bodies. (shrink)