Abstract
In "Action and Responsibility,'' Joel Feinberg pointed to an important idea to which he gave the label "the accordion effect.'' Feinberg's discussion of this idea is of interest on its own, but it is also of interest because of its interaction with his critique, in his "Causing Voluntary Actions,'' of a much discussed view of H. L. A. Hart and A. M. Honoré that Feinberg labels the "voluntary intervention principle.'' In this essay I reflect on what the accordion effect is supposed by Feinberg to be, on differences between Feinberg's understanding of this idea and that of Donald Davidson, and on the interaction between Feinberg's discussion of the accordion effect and his critique of the voluntary intervention principle.