The Theory Theory (TT) versus Simulation Theory (ST) debate is primarily concerned with how we understand others’ mental states. Theory theorists claim we do this using rules that are akin to theoretical laws, whereas simulation theorists claim we use our own minds to imagine ourselves in another’s position. Theorists from both camps suggest a consideration of individuals with autism spectrum disorders (ASD) can help resolve the TT/ST debate (e.g., Baron-Cohen 1995; Carruthers 1996a; Goldman 2006). We present a three-part argument that (...) such research has so far been inconclusive and that the prospects for studies of ASD to resolve the debate in the near future remain uncertain. First, we discuss evidence indicating that some individuals with ASD can perform effectively on tests of mental state understanding, which questions what ASD can tell us regarding theorising or simulation. Second, we claim that there is compelling evidence that domain-general mechanisms are implicated in mental state reasoning, which undermines how ASD might inform the TT/ST debate given that both theories appeal to domain-specific mindreading mechanisms. Third, we suggest that neuroscientific evidence for an assumed role of the mirror neuron system in autism also fails to arbitrate between TT and ST. We suggest that while the study of ASD may eventually provide a resolution to the TT/ST debate, it is also vital for researchers to examine the issues through other avenues, for example, by examining people’s everyday counterfactual reasoning with mental state scenarios. (shrink)