Published in 1897, The Evolution of the Idea of God is a study of humans’ belief in God from primitive tribal religions to what Allen considered the more advanced Christian view. The main question explored here is “How did we arrive at our knowledge of God?” Rather than trying to prove or disprove any claims about the divine, Allen’s method simply traces the psychological processes that led humans to religious belief, and further, from a belief in polytheism to monotheism.