""A Reply to Harnack on the Essence of Christianity"" is a philosophical work by Hermann Cremer, originally published in 1903. The book responds to Adolf von Harnack's influential work ""What is Christianity?"" and offers a critique of Harnack's understanding of the essence of Christianity. Cremer argues that Harnack's view of Christianity as a purely ethical and social movement is insufficient, and that the true essence of Christianity lies in its...