 Examples like those just described show that if we wish to follow Menzies and Price in defending the claim that if an association between \(A\) and \(B\) persists when \(A\) is given the right sort of “independent causal history” or is “manipulated” in the right way, then \(A\) causes \(B\), we need to be much more precise by what we mean by the quoted phases. There have been a number of attempts to do this in the recent literature on causation. The basic idea that all of these discussions attempt to capture is that of a “surgical” change in \(A\) which is of such a character that if any change occurs in \(B\), it occurs only as a result of its causal connection, if any, to \(A\) and not in any other way. In other words, the change in \(B\), if any, that is produced by the manipulation of \(A\) should be produced only via a causal route that goes through \(A\). Manipulations or changes in the value of a variable that have the right sort of surgical features have come to be called interventions in the recent literature (e.g., Spirtes, Glymour, and Scheines 2000; Meek and Glymour 1994; Hausman 1998; Pearl 2009; Woodward 1997, 2000, 2003; Woodward and Hitchcock 2003; Cartwright 2003) and I will follow this practice. The characterization of the notion of an intervention is rightly seen by many writers as central to the development of a plausible version of a manipulability theory. One of the most detailed attempts to think systematically about interventions and their significance for understanding causation is due to Pearl 2009 and I turn now to a discussion of his views.