In the last half of the 20th century, a consensus emerged that Christian theology in the Western tradition had failed to produce a viable doctrine of the Holy Spirit, and that Augustine's trinitarian theology bore the blame for much of that failure. This book offers a fresh rereading of Western trinitarian theology to better understand the logic of its pneumatology. Ables studies the pneumatologies of Augustine and Karl Barth, and argues that the vision of the doctrine of the Spirit in these theologians should be understood as a way of talking about participating in the mystery of God as a performance of the life of Christ. He claims that for both theologians trinitarian doctrine encapsulates the grammar of the divine self-giving in history. The function of pneumatology in particular is to articulate the human reception and enactment of God's self-giving as itself part of the act of God; this "self-involving" logic is the special grammar of the doctrine of the Holy Spirit.