Gould addresses the conflict between secular scientists and religious believers who question or deny scientific theory when it is in discrepancy with religious teachings on the origin and nature of the natural world. Borrowing a term from the Catholic Church, Gould describes science and religion as each comprise a separate magisterium of human understanding. Science defines the natural world, and religion the moral world. If each realm is separate, then according to Gould, they are not in conflict. He calls this the principle of non-overlapping magisteria, abbreviated NOMA.