 And here is  RES+REU’s  third virtue. So far, we have said that “mental simulation” can either pick out a dyadic relation between mental states or a monadic property of mental states. In fact, its ambiguity runs deeper than this, since philosophers and cognitive scientists also use “mental simulation” to refer to a monadic property of cognitive processes, namely, the property being a (mental) simulation process (or: “process of mental simulation”, “simulational process”, “simulative process”, etc.) As a first stab, a (mental) simulation process is a cognitive process generating simulated mental states.  RES+REU  has the resources to capture this usage of “mental simulation” too. Indeed,  RES+REU implicitly contains the following definition of “simulation process”: