The relationship between the Father and the Son in the Trinity has been hotly debated since the earliest centuries of the church. The Church Fathers like Tertullian, Athanasius and Hilary of Poiters wrestled with it; church councils at Nicaea, Syrmium and Chalcedon legislated about it in attempts to define orthodoxy and heresy. What did they and the Bible say, and why does it matter today? The contemporary implications are wider than you might realise, touching on matters as diverse as the ordination of women, male-female relations, the certainty of salvation and the nature of power,...