Unity without diversity is, at best, boring, and at worse, totalitarian. Diversity without unity constantly threatens to degenerate, at best, into tensions and failures at cooperation and, at worst, into genocide. The sources of diversity in the United States are many. Racial and ethnic differences as well as differences based on national origins, social class, region, neighborhood, and sexual orientation all come readily to mind. Common ideals and beliefs such as democracy, freedom, and equal rights for all are sources of unity. The American experience has been as successful as it has because there is much that divides the people, leading to dynamic change and a creative restlessness, and because there is much that unites the people, leading to the acceptance of a shared, or communal, responsibility. However, to complete the picture and to understand both the rich diversity of American society and the unity of American society, religion and its role in society must also be taken into account. Any attempt to understand American society that disregards the contribution religion makes to both the diversity and the unity of American society will be fundamentally flawed. In this essay, first, the author notes the pervasiveness of religion in American society and how it contributes to both diversity and unity. Second, he considers how the understanding of church-state separation can either acknowledge and value the role of religion in society, or can ignore and stifle what religion has to contribute to a diverse, yet united, society.