This book addresses one of the most contested issues in contemporary Christian the nature of Christ’s atoning work on the cross. Penal Substitutionary Atonement (PSA) is frequently criticized—particularly within Catholic and Eastern Orthodox circles—as a product of a narrow philosophical framework foreign to the theology of the Church Fathers. Closely related models, such as Vicarious Satisfaction (VS), are likewise often dismissed, especially in the East. Challenging these assumptions, this work argues that PSA, when properly defined, is neither novel nor theologically alien. Instead, it is deeply embedded in the soteriological reflections of both the Latin and Greek Fathers across the first millennium of Christianity. The study further strengthens its case through engagement with the theology of St. Thomas Aquinas, the Doctor Communis (Common Doctor) of the Catholic Church, as well as authoritative texts from the Eastern Orthodox tradition, demonstrating that penal and vicarious dimensions of Christ’s atonement are firmly rooted in the shared patristic heritage of the Church.