 The basic structure of the argument for Anomalous Monism is as follows. We start with the plausible assumption that some mental events, such as believing that it is raining, are caused by certain physical events, in this case the rain. Similarly, it is assumed that some physical events, such as one’s arm rising, are caused by certain mental events, such as deciding to scratch one’s head. Davidson calls this the Principle of Causal Interaction; we shall call it the interaction principle: