There is a debate going on in the contemporary philosophical literature concerned with our folk-psychological capacities, that is, how we explain, predict and interpret the behavior of others, and how we ascribe mental states such as beliefs and desires to each other. The purpose of this thesis is to examine the status of the two opponents of this debate, simulation theory and theory-theory, concerning the plausibility of their explanation of self knowledge, our capacity to attribute mental states to ourselves and to each other. A preliminary concern is to determine whether or not simulation theory should be considered a plausible rival to theory-theory, the presently dominant theory of our folk psychological capacities.