The theory-theory is not supported by evidence in the everyday actions of infants and toddlers whose lives a Theory of Mind is meant radically to transform. This paper reviews some of these challenges to the theory-theory, particularly from communication and deception. We argue that the theory’s disconnection from action is both inevitable and paradoxical. The mind–behaviour dualism upon which it is premised requires a conceptual route to knowing minds and disallows a real test of the theory through the study of action. Taking engagement seriously avoids these problems and requires that both lay people and psychologists be participants rather than observers in order to know, and indeed to create, minds.