 Let’s now go back to  REU.  The main idea behind it is that whether a mental state is a mental simulation of another mental state depends on the cognitive processes generating these two mental states, and on the cognitive mechanisms implementing such cognitive processes. More precisely, in order for mental state M* to be a mental simulation of mental state M, it has to be case that: (i) cognitive processes P* and P, which respectively generate M* and M, are both implemented by the same (type of) cognitive mechanism C; (ii) P is implemented by the use of C, while P* is implemented by the reuse of C. 