The Psalms constitute one of the most established fields within Old Testament scholarship. Their influence, however, extends far beyond exegesis, reaching into practical theology, liturgy, music, poetry, and visual culture. The question of whether the Psalter also challenges systematic theology at its core has rarely been addressed in depth. This study sets out to explore precisely that issue. In twenty carefully elaborated steps, Günter Bader develops a theology of the Psalter that integrates historical, practical, and systematic perspectives. Beginning with the traditional title "The Psalter," he situates the work within a wide-ranging history of reception from premodernity through modernity. By tracing the ways in which the Psalms have shaped devotional practice, liturgical forms, and artistic expression, he shows at the same time how they have influenced central theological concepts. The study culminates in the thesis that theology cannot be conceived adequately without the Psalter. Far from belonging only to the domain of exegesis, the Psalter thus emerges as a constitutive element of theological reflection as such. With its rigorous analysis and innovative framework, the author provides a new foundation for connecting biblical tradition with systematic inquiry. He thereby enriches both exegetical and theological research and opens perspectives that will prove essential for ongoing academic debate.