 The interaction principle states that some mental events causally interact with some physical events. In this section we will look briefly at a number of issues related to this principle: how mental and physical events are demarcated, the nature of events themselves, the scope of the interaction principle, the relationship between mental events and causation, and the use of the interaction principle in establishing one component of mental anomalism—psychological anomalism, according to which there can be no strict, purely psychological laws. Psychological anomalism is to be distinguished from psychophysical anomalism, which holds that there can be no strict psychophysical laws. This latter thesis will be explored in detail in our discussion of the anomalism principle  (4).