Rudolf Otto was an eminent German Lutheran theologian, philosopher, and comparative religionist. He is regarded as one of the most influential scholars of religion in the early twentieth century and is best known for his concept of the numinous, a profound emotional experience he argued was at the heart of the world's religions. While his work started in the domain of liberal Christian theology, its main thrust was always apologetical, seeking to defend religion against naturalist critiques. Otto eventually came to conceive of his work as part of a science of religion, which was divided into the philosophy of religion, the history of religion, and the psychology of religion.

Comparative religion is the branch of the study of religions with the systematic comparison of the doctrines and practices, themes and impacts of the world's religions. In general the comparative study of religion yields a deeper understanding of the fundamental philosophical concerns of religion such as ethics, metaphysics and the nature and forms of salvation. It also considers and compares the origins and similarities shared between the various religions of the world. Studying such material facilitates a broadened and more sophisticated understanding of human beliefs and practices regarding the sacred, numinous, spiritual and divine.