We will study children’s thinking about what phenomena exist and what outcomes are possible across two different domains: religion and science. Our previous work has uncovered parallels and differences in how young children think about these two domains. Children conceptualize unobservable religious entities (e.g., souls) and scientific entities (e.g., bacteria) similarly. They are confident that both types of entities exist (despite not having observed them) and often cite the causal properties of the entity to justify their beliefs. Nevertheless, we have also found that children with a religious rather than a secular upbringing have a different conception of what is and is not possible. They are willing to consider that natural causal laws might not impose ultimate constraints on reality. Our proposal asks three over-arching questions. (1) Do these early patterns of thinking remain stable with age, or do they change as children get older and interact with the wider community? (2) How are these early parallels and differences established? We will observe parent-child discussions to discern how beliefs about religious and scientific phenomena are transmitted across generations. (3) How far does the pattern of development amongst U.S. children reflect the pluralistic nature of U.S. society, i.e., a society in which children are typically exposed to diverse views, religious as well as secular? We plan to compare children growing up in the U.S. with children growing up in two contrasting countries – in Iran, a theocracy where religion has a pervasive impact on government and education and China, a communist state where secularism predominates throughout public life. Project outcomes include articles for academic and lay audiences and an interdisciplinary conference on children’s religious and scientific development. We anticipate that our findings will help to expand the dialogue between science and religion, in keeping with Sir John Templeton’s mission.