 Suppose that we agree that any plausible version of a manipulability theory must make use of the notion of an intervention and that this must be characterized in causal terms. Does this sort of “circularity” make any such theory trivial and unilluminating? It is arguable that it does not, for at least two reasons. First, it may be, as writers like Woodward (2003) contend, that in characterizing what it is for a process \(I\) to qualify as an intervention on \(X\) for the purposes of characterizing what it is for \(X\) to cause \(Y\), we need not make use of information about the causal relationship, if any, between \(X\) and \(Y\). Instead, it may be that we need only to make use of other sorts of causal information, e.g., about the causal relationship between \(I\) and \(Y\) or about whether \(I\) is caused by causes that cause \(Y\) without causing \(X\), as in  (M1)–(M4)  above. To the extent that this is so, we may use one set of claims about causal relationships (e.g., that \(X\) has been changed in a way that meets the conditions for an intervention) together with correlational information (that \(X\) and \(Y\) remain correlated under this change) to characterize what it is for a different relationship (the relationship between \(X\) and \(Y)\) to be causal. This does not yield a reduction of causal talk to non-causal talk, but it is also not viciously circular in the sense that it presupposes that we already have causal information about the very relationship that we are trying to characterize. One reason for thinking that there must be some way of characterizing the notion of an intervention along the lines just described is that we do sometimes learn about causal relationships by performing experiments—and it is not easy to see how this is possible if to characterize the notion of an intervention on \(X\) we had to make reference to the causal relationship between \(X\) and its effects.