Theory of Mind is the ability to attribute mental states to oneself and others. Premack and Woodruff (1978) argued that such commonsense mentalism requires theoretical knowledge because mental states are unobservable and inferred like theoretical terms in the sciences. Mental state attribution improves the everyday explanations and predictions of human behavior, therefore the conceptual system underlying these attributions has the explanatory power of a theory. However, the term “theory” is often used loosely, in the sense of a coherent body of knowledge. Theory of Mind research has been an extraordinarily productive area of conceptual development since the 1980s (see Astington, Harris, & Olson, 1988; Baron-Cohen, Tager-Flusberg, & Cohen, 1994; Carpendale & Lewis, 2004; Flavell, 2000; Lewis & Mitchell, 1994; Perner, 1991; Sodian, 2005; Wellman, 1990, 2011, 2014 for books and review chapters).