"The Essence of Christianity" by Ludwig Feuerbach is a philosophical work published in 1841. It argues that God is not a separate being but rather an outward projection of human nature and needs. Feuerbach contends that every divine quality attributed to God actually corresponds to human features, making religion a mirror of humanity rather than a revelation from above. This influential critique of religion shaped later thinkers including Marx and Engels, establishing Feuerbach's theory of alienation and cementing the work as a classic of humanist philosophy.
Wikipedia page about this book: en.wikipedia.org/wiki/The_Essence_of_Christianity