In the manner of the eighteenth-century philosopher, Freud argued that religion and science were mortal enemies. Early in the century, he began to think about religion psychoanalytically and to discuss it in his writings. The Future of an Illusion (1927), Freud's best known and most emphatic psychoanalytic exploration of religion, is the culmination of a lifelong pattern of thinking.

Freud uses his understanding of psychology to examine the roots of both civilization and religion. This takes the form of a comprehensive essay, with Freud forming an argument throughout its chapters about the history of religion and the part it should play in society's future.