Causal scope, the number of different effects a cause can produce, is a salient feature of causes. In the present research, we address the question whether reasoners use causal scope as a diagnostic cue to infer the strengths of individual causal links. In three experiments, we manipulated the number of effects of a cause, and asked subjects to assess the causal strengths of single causal links. The results document a clear influence of causal scope on perceived link strength. In particular, subjects tended to display a ``dilution” effect. They perceived a causal link to be weaker if that link belonged to a cause that is capable of producing additional effects. This dilution effect can be explained by a dispositional notion of causality according to which a cause possesses a certain amount of causal power or capacity that it distributes cross its different causal pathways.