The chapter uses the principle according to which difference-making or counterfactual dependence is sufficient for causation to show that there are physical effects of mental causes. If non-reductive physicalism is true, applying the principle is straightforward. The principle also yields higher-level causes that are not mental but might be considered problematic. These causes are best diagnosed as causes that have little explanatory relevance. If dualism is true, applying the principle about causation in order to show the existence of mental causation is less straightforward, but still possible. In order to avail themselves of the principle, dualists need to assume that the laws that connect the mental and physical realms have a special status. Rival approaches according to which mental causation or human agency require the transference of a physical quantity or of a power are in conflict with empirical results. The account of mental causation by counterfactual dependence, by contrast, squares with these results.

The chapter deals with the exclusion problem. How can mental events have physical effects if these effects already have physical causes? Even if this is possible in principle, would this not yield a situation like in a firing squad, where the victim’s death is overdetermined by the firings of the squad members? And would it not be implausible that the situation is like this whenever there is mental causation? If a difference-making approach to causation is adopted, these questions can be answered in a satisfactory way. Although mental and physical causes might nominally overdetermine their physical effects, cases of mental causation are sufficiently dissimilar to typical cases of overdetermination not to be problematic. Unlike in cases of mental causation (on the account offered here), in typical cases of overdetermination, the individual causes do not make a difference to the effect. The exclusion problem is harder to solve if it is formulated in terms of sufficient causes, but no commitment to sufficient causation follows from the account of mental causation in terms of difference-making.