 This argument is surely the briefest of those against epiphenomenalism, but it may have been more persuasive than any other. Epiphenomenalists, however, can make the following reply. First, it can never be obvious what causes what. Animated cartoons are full of causal illusions. Falling barometers are regularly followed by storms, but do not cause them. More generally, a regularity is causal only if it is not explained as a consequence of underlying regularities. It is part of epiphenomenalist theory, however, that the regularities that we observe to hold between mental events and actions can be explained by underlying regularities. Schematically, suppose physical event \(P_1\) causes both mental event \(M\) and physical successor \(P_2\), as in Figure 1.