Why did Christ have to die for us? In this book Sungkyu Joo addresses that enduring question by looking beyond isolated theories of the atonement and turning instead to the doctrine of the Trinity itself. While many modern discussions focus on the cross alone, the author argues that Christ's saving death can only be properly understood within the eternal relationship between the Father and the Son. Drawing on the classical insights of Augustine, Calvin, and Turretin, the book shows how their shared Trinitarian framework provides a coherent and compelling foundation for understanding why Christ's atoning work was not accidental or arbitrary, but hypothetically necessary. At the same time, Sungkyu Joo explains why alternative approaches especially those associated with anti-Trinitarian thinkers such as Servetus and Socinus ultimately fail to offer a stable account of Christ's atoning work. By weakening the natural and personal relationship within God or introducing hierarchy into the divine life, these views undermine the very conditions required for a free and spontaneous act of salvation. In contrast, the classical and Reformed tradition presents a holistic concept of God in which the natural generation of the Son and the Trinity's spontaneous wills work together rather than against each other. Written out of both pastoral concern and academic study, this book offers a clear and accessible defense of Christ's vicarious satisfaction as a necessary expression of God's triune life and saving love.

Why did Christ have to die for us? In this book Sungkyu Joo addresses that enduring question by looking beyond isolated theories of the atonement and turning instead to the doctrine of the Trinity itself. While many modern discussions focus on the cross alone, the author argues that Christ's saving death can only be properly understood within the eternal relationship between the Father and the Son. Drawing on the classical insights of Augustine, Calvin, and Turretin, the book shows how their shared Trinitarian framework provides a coherent and compelling foundation for understanding why Christ's atoning work was not accidental or arbitrary, but hypothetically necessary. At the same time, Sungkyu Joo explains why alternative approaches especially those associated with anti-Trinitarian thinkers such as Servetus and Socinus ultimately fail to offer a stable account of Christ's atoning work. By weakening the natural and personal relationship within God or introducing hierarchy into the divine life, these views undermine the very conditions required for a free and spontaneous act of salvation. In contrast, the classical and Reformed tradition presents a holistic concept of God in which the natural generation of the Son and the Trinity's spontaneous wills work together rather than against each other. Written out of both pastoral concern and academic study, this book offers a clear and accessible defense of Christ's vicarious satisfaction as a necessary expression of God's triune life and saving love.