Four interrelated themes recur throughout the volume. One concerns the descriptive picture for the target of study: What is the nature of theory of mind across different parts of the life span? In particular, how does the study of advanced developments add to the well-documented achievements of the first 5 years? A second theme addresses how to explain the developmental changes that are observed, both the commonalties that characterize development and individual differences in the speed or the extent of mastery. The third theme examines the effects of theory of mind on other aspects of development, and a final theme is the theoretical question of how best to characterize advanced theory of mind, namely whether theories designed to explain early developments can be successfully extended to more advanced forms of understanding.