Carl Trueman analyses the theology of the great Puritan theologian, John Owen, paying particular attention to his vigorous trinitarianism. To understand Owen, we need to see him as a seventeenth-century representative of the Western trinitarian and anti-Pelagian tradition. Trueman demonstrates how Owen used the theological insights of patristic, medieval, and Reformation theologians to meet the challenges posed to Reformed Orthodoxy by his contemporaries. A picture emerges of a theologian whose thought represented a critical reappropriation of aspects of the Western tradition for the purpose of developing a systematic restatement of Reformed theology capable of withstanding the assaults of both the subtly heterodox and the openly heretical.