Karl Barth argued for a more satisfactory theology of the Holy Spirit, yet classical theism has so far failed to meet this demand. Pneumatology has been treated as a mere appendage to the doctrine of God, neglecting the fact that "an understanding of the unique personhood of the Spirit is ... decisive for the understanding of God in general" (Jürgen Moltmann).
The Lord is the Spirit addresses these gaps in Trinitarian theology by reconsidering the doctrine of God from a pneumatological vantage point. This approach recovers an emphasis on divine immanence – God's interaction with humanity – which has been marginalised in favour of divine transcendence. This critique tackles the need to account for the Trinity in its totality by stressing the identity of God as Father, Son and Holy Spirit from an evangelical and Pentecostal perspective, while engaging in ecumenical dialogue with a wide spectrum of historical and contemporary theological voices. In a much-needed revision to classical theism, Gabriel convincingly argues that the integration of pneumatology into the doctrine of divine attributes will retrieve divine immanence from the theological margins it has so far occupied.