 The argument that epiphenomenalism is self-stultifying in the way just described rests on the premise that knowledge of a mental event requires causation by that mental event. But epiphenomenalists may reject that premise without absurdity. One way of seeing how to do this involves considering the interactionist diagram in Figure 2, which shows \(P_1\) as directly causing \(M\) but not \(P_2\), and \(M\) directly causing \(P_2\).  (Directly causing is an intransitive relation. Causation (when used without modifier) is transitive: events are causally related if there is a chain of direct causes, however long, that connects them.)