Is our understanding of the mind to be explained in terms of our mastering a theory, or in terms of a general capacity for simulating other agents? The first type of theory, called the ?Theory Theory?, claims that children learn how to understand and predict other people?s psychological states in a way that closely parallels how they learn physical and biological facts. They posit unobservable theoretical entities (mainly beliefs and desires) in order to explain observed facts (mainly behaviour), master the inferential relations between them in a given domain, and learn how to apply the resulting concepts to new cases within the domain. There has been no consensus among the developmental psychologists and philosophers involved in this debate as to the role respectively attributed to experience and to innate constraints on mentalising. Some of the main proponents of the idea of a Theory Theory of mind have hypothesised that children rely both on experience and on their general reasoning capacities to produce folk-psychological explanations.1 Others have claimed that theory of mind originates in a domain-specific module that comes to fruition at around 2 years of age.2 This module is taken to consist in a metarepresentational knowledge structure that allows children to represent facts about propositional attitudes by ?decoupling? a primary representation, with its usual reference, from a secondary representation, whose reference depends on its specific role in the context of a pretence, belief, etc. While the Theory Theory of mental concept acquisition takes its inspiration from an analogy with the case of linguistics (in its modular version) or with general scientific procedures (in its non-modular version), the second type of theory, called ?Simulation Theory?, arises fromtwo independent sets of considerations. One is the kind of philosophical consideration associated with the principle of charity: to understand others necessarily presupposes viewing them as thinking and rationally evaluating situations as I do.