There is strong evidence that developments in children's theory of mind (ToM) at 3?4 years are related to developments in language and executive function. However, these relationships might exist for 2 reasons. First, language and executive function might be necessary for the mature ToM abilities that children are in the process of developing. Second, language and executive function may be necessary for developing ToM but have no necessary role in mature ToM. It is difficult to distinguish between these possibilities if researchers only study young children. Studies of adults can provide direct evidence about the role of language and executive function in mature ToM. Recent work suggests that impaired executive function has multiple roles in adult ToM but that severely impaired grammar can leave ToM structurally intact. While studies of children report that ToM correlates with both language and executive function, findings from adults suggest that these relationships should be interpreted in importantly different ways.