 As we have seen, Menzies and Price assign a central role to “free action” in the elucidation of causation. They do not further explain what they mean by this phrase, preferring instead, as the passage quoted above indicates, to point to a characteristic experience we have as agents. It seems clear, however, that whether (as soft determinists would have it) a free action is understood as an action that is uncoerced or unconstrained or due to voluntary choices of the agent, or whether, as libertarians would have it, a free action is an action that is uncaused or not deterministically caused, the persistence of a correlation between \(A\) and \(B\) when \(A\) is realized as a “free act” is not sufficient for \(A\) to cause \(B\). Suppose that, in the example described above, the position of the barometer dial \(X\) is set by a free act (in either of the above senses) of the experimenter but that this free act (and hence \(X)\) is correlated with \(Z\), the variable measuring atmospheric pressure, perhaps because the experimenter observes the atmospheric pressure and freely chooses to set \(X\) in a way that is correlated with \(Z\). (This possibility is compatible with the experimenter’s act of setting \(X\) being free in either of the above two senses.) In this case, \(X\) will remain correlated with \(Y\) when produced by a free act, even though \(X\) does not cause \(Y\). Suppose, then, that we respond to this difficulty by adding to our characterization of \(A\)’s being realized by a free act the idea that this act must not itself be correlated with any other cause of \(A\). (Passages in Price 1991 suggest such an additional proviso, although the condition in question seems to have nothing to do with the usual understanding of free action.) Even with this proviso, it need not be the case that \(A\) causes \(B\) if \(A\) remains correlated with \(B\) when \(A\) is produced by an act that is free in this sense, since it still remains possible that the free act that produces \(A\) also causes \(B\) via a route that does not go through \(A\). As an illustration, consider a case in which an experimenter’s administration of a drug to a treatment group (by inducing patients to ingest it) has a placebo effect that enhances recovery, even though the drug itself has no effect on recovery. There is a correlation between ingestion of the drug and recovery that persists under the experimenter’s free act of administering the drug even though ingestion of the drug does not cause recovery.