In his works, the first Latin Christian author, Quintus Septimius Florence Tertullian (150/170-220/240), battles pagans, heretics and human imperfection. In the treatise offered to readers, he attacks the Gnostic Marcion, who saw a fundamental difference between the Old and New Testaments and developed the doctrine of the harsh God of the first and the good God of the second. The essay “Against Marcion” is a refutation of Gnostic dualism, a theodicy of the Creator, a proof of the organic connection between the Old and New Testaments, and an interpretation of a huge number of biblical texts. The five books of this treatise contain almost all the main provisions of Christianity and serve as a kind of textbook on sect studies and on the Holy Scriptures of both Testaments. Tertullian here defends, among other things, the truth of the incarnation, suffering, death of the Savior predicted by the Old Testament prophets and defends the resurrection of the dead. The passion of Quintus Septimius, his conviction that he was right and his desire to turn his readers away from a dangerous error at any cost inspire respect and make us wonder whether the fire of living faith has weakened in people over the last 18 centuries, whether indifference and conformism, proudly called tolerance, have taken possession of us. everyone interested in church history, theology and ancient culture.