The doctrine of the Spirit of truth (cf. John 16:13) stands at the center of Hans Urs von Balthasar on Spirit and Truth. To articulate a coherent systematic theology of this aspect of pneumatology, Gunnar Innerdal analyzes Balthasar's Theo-Logic and related texts, followed by critical assessments in connection to the theoretical framework of Lorenz B. Puntel's structural-systematic philosophy and in dialogue with other contemporary theological proposals. In Part I philosophical questions concerning truth are discussed. Part II shows the relevance of Christology and Trinity for theological truth talk, discussing the doctrine of analogy and negative theology. Part III elaborates on the relationship of Son and Spirit, and the Spirit's work as the Spirit of truth inside and outside the Church. The Spirit, as breath of life and Spirit of Christ, has ontological and epistemological significance for all truth.