 I will not attempt to adjudicate here among these and various other proposals concerning the best way to characterize the notions of intervention and causal effect. Instead, I want to comment on the general strategy they embody and to compare it with the approach to causation associated with theorists like Menzies and Price. Note first that the notion of an intervention, when understood along either of the lines described above, is an unambiguously causal notion in the sense that causal notions are required for its characterization—thus the proposals variously speak of an intervention on \(X\) as breaking the causal connection between \(X\) and its causes while leaving other causal mechanisms intact or as not affecting \(Y\) via a causal route that does not go through \(X\). This has the immediate consequence that one cannot use the notion of an intervention to provide a reduction of causal claims to non-causal claims. Moreover, to the extent that reliance on some notion like that of an intervention is unavoidable in any satisfactory version of a manipulability theory (as I believe that it is), any such theory must be non-reductionist. Indeed, we can now see that critics who have charged manipulability theories with circularity have in one important sense understated their case: manipulability theories turn out to be “circular” not just in the obvious sense that for an action or event \(I\) to constitute an intervention on a variable \(X\), there must be a causal relationship between \(I\) and \(X\), but in the sense that \(I\) must meet a number of other causal conditions as well.