Loisy's book was originally written as a response to Adolf von Harnack's What is Christianity? Its importance revolves around both the crucial debate with Harnack and the intrinsic merit of its own scholarly position. Loisy's The Gospel and the Church serves to remind Catholics of their own inherited past and offers a view of the Protestant past from the point of view of an outsider. For the Protestant reader in particular, it offers an alternative view to Protestant understanding of the relationship of Jesus to the Church.