The purpose of Briggman's study is to provide an in-depth examination of Irenaeus' pneumatology, to demonstrate that his pneumatology consists of a combination of Jewish traditions with New Testament doctrine, and to argue that Irenaeus was the first author to construct a theological account structured around a Trinitarian, rather than binitarian, logic that does not diminish the Holy Spirit's identity and activity. After outlining the prevailing binitarian logic of second-century theology in the first chapter, Briggman proceeds to examine what he perceives to be the distinctiveness of Irenaeus' pneumatology, particularly as articulated in Against heresies. Briggman argues that a progression in Irenaeus' understanding of the Holy Spirit can be traced through that work, from elementary expressions in Against heresies 1 and 2 to the blossoming of a complex and nuanced pneumatology in the final three books. Briggman draws especial attention to the ways in which Irenaeus emphasises the distinctive identity and activity of the Holy Spirit. Thus, in Against heresies 3, Irenaeus highlights the Spirit's role in governing the preservation and spread of the Gospel; the Spirit's anointing of Jesus' humanity for the accomplishment of his mission; the ecclesiological role of the Spirit in uniting individuals to itself, to Christ, and to each other; and the agency of the Spirit in creation that enables created beings to come to knowledge of God's love. In Against heresies 4 Irenaeus reveals the Jewish character of his pneumatology by identifying the Spirit as Wisdom and as one of the Hands of God, thereby securing the Spirit's divinity by ascribing creative agency to Spirit. Briggman argues, moreover, that this identification distinguishes the Spirit from the Father and the Son in a manner that preserved a Trinitarian structure to his theology. Finally, in Against heresies 5, Irenaeus emphasises the instrumentality of the Holy Spirit as the source of temporal and eternal life, thereby articulating an understanding of how humanity attains to eternal life that revolves around the work of the Holy Spirit. In sum, Briggman submits that Irenaeus articulated a sophisticated and complex pneumatology that eclipsed previous understandings of the Holy Spirit, and that served as the apex of pneumatological thought until the fourth century. Briggman's analysis of Irenaeus' pneumatology is insightful and thorough. The arguments contained in this study are painstakingly constructed, developed through close and careful analysis of the Irenaean texts and in conversation with a wealth of Irenaean scholarship. Irenaeus of Lyons and the theology of the Holy Spirit is an important contribution to our understanding of Irenaeus' theology, as well as to our understanding of early Christian pneumatology.