This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Adolf von Harnack's 1900 Berlin lecture series, published as What Is Christianity?, reduced the essence of the gospel to three themes, the fatherhood of God, the infinite value of the human soul, and the higher righteousness of love, a documented distillation distinct from a comprehensive survey of Christian doctrine across its historical development. Harnack, a student of Albrecht Ritschl's Liberal Theology and by then a professor at Berlin, framed those three themes as what remained once later dogmatic accretion, layered onto what he judged a simpler original message, was stripped away.
That stripping down is documented as an act of historical criticism rather than of doctrinal invention, consistent with Harnack's wider standing as a historian of dogma who traced how Christian teaching had accumulated its later theological elaboration over centuries. The lectures are recorded as marking the turn of the century height of Liberal Theology's confidence in historical criticism as the route to Christianity's true kernel, a documented high point of a method rather than its starting point, since Harnack was building on Ritschl's own earlier relocation of theology onto historical and ethical ground.
That a historian of dogma could reduce an entire tradition's accumulated doctrine to three themes, presented as a recovered original core rather than a new teaching, and have the result stand as Liberal Theology's best known statement marks What Is Christianity? as a documented case where historical criticism's own confidence reached its clearest, most quoted expression.