These papers explore the teachings of writers from both east and west on the nature and activity of the Holy Spirit. Brendan Leahy, ‘“Hiding behind the works”: the Holy Spirit in the Trinitarian rhythm of human fulfilment in the theology of Irenaeus’, presents the Holy Spirit's work in soteriology and anthropology. Janet E. Rutherford, ‘The Alexandrian spirit: Clement and Origen in context’, defends Rufinus' rendering of On first principles and proposes the relevance of Christian Platonism today. Lewis Ayres, ‘The Holy Spirit as the “undiminished giver”: Didymus the Blind's De spiritu sancto and the development of Nicene pneumatology’, argues that Didymus offers one of the earliest and most developed arguments for the Spirit's divinity, namely that the Spirit's role as sanctifier implies an identity with the one eternal source of sanctification. According to ‘Cyril of Jerusalem on the Holy Spirit’ by Juliette Day the gift of the Holy Spirit and sealing occurred at the immersion and not after it; Cyril opposed the Tropici also refuted by Athanasius. Thomas O'Loughlin discusses ‘St Augustine's view of the place of the Holy Spirit in the formation of the Gospels' under four headings: answering objections to the claim of uniqueness for Christianity, relating the Spirit to the work of Christ, the Spirit acting in the work of the Apostles and Evangelists, and invoking the Spirit to make sense of difficulties in the Gospels. Finbarr G. Clancy, ‘The Holy Spirit, the Trinity and the eucharist in St Fulgentius of Ruspe's Ad Moninum, book 2’, discusses Fulgentius' reply to the problem, ‘If a sacrifice is offered to the Holy Trinity, why is the sending of the Holy Spirit only asked for?’ Serafim Seppälä, ‘The Holy Spirit in Isaac of Nineveh and east Syrian mysticism’, notes that in Isaac's corpus there is no discussion of the Holy Spirit's position in the Trinity, but the activity of the Holy Spirit is the divine reality behind the mystical life. Andreas Andreopoulos in ‘The Holy Spirit in the ecclesiology of Photios of Constantinople’ points out that the dispute about the filioque was primarily about ecclesiology. Gregory Collins's paper on ‘Three modern “Fathers” on the filioque: good, bad or indifferent?’ identifies the eastern view that the filioque obscured the difference between the mission of the Spirit in the economy of salvation and his eternal procession within the inner life of the Godhead; it was found good by Karl Barth, bad by Vladimir Lossky, and as more than an opinion but less than a dogma by Sergei Bulgakov. Patrick Mullins ocarm, ‘The Holy Spirit and the Marian typology of St Ambrose at Vatican II’, explores the comparison that Ambrose made between Mary's virginal motherhood of the Son of God and the Church's virginal motherhood of disciples through Christian initiation. This volume maintains a consistent quality often absent in collected essays and deserves a place in the bibliography of standard works on the Holy Spirit. The only index is of proper names.