Ludwig Feuerbach (1804—1872) was a famous German philosopher and atheist. The founder of psychoanalysis Freud heavily borrowed from his book Essence of Christianity to create The Future of an Illusion. What are often thought of as "Freudian" terms are in fact Feuerbachian. Such borrowings can be seen in the words and passages of Essence of Christianity: "wish-fulfillment"; "What man misses—whether this be articulate and therefore conscious, or an unconscious need—that is his God"; "Man projects his nature into the world outside himself before he finds it in himself"; "To live in projected dream-images is the essence of religion. Religion sacrifices reality to the projected dream."  Karl Marx also borrowed from Essence of Christianity, most famously the idea that "religion is the opium of the masses."
- Faith of the Fatherless: The Psychology of Atheism, Paul C. Vitz, (Spence Publishing Company, 1999)