The introduction looks at the different ways that the unique, but troublesome, injunction at the heart of the Sermon on the Mount for the followers of Jesus to ‘Be perfect, therefore, as your heavenly Father is perfect’ (Matt. 5.48) has been interpreted within Christian history. It looks specifically at the interpretations of John and Charles Wesley, John Calvin, Thomas Aquinas, Augustine of Hippo, Gregory of Nyssa and Tertullian and argues that Aquinas’ is the most sophisticated. It suggests how each reflects the influence of their particular social contexts and their radically different theological takes on humanity, while holding in common a clear distinction between human and divine perfection.

Chapter 5 turns, at last, to the more conventional resource for Christian ethics, namely the Bible. It looks specifically at the way that teleios and teleioö (adjective and verb) are used thrice each in Matthew, in Paul and in Pauline letters, but most frequently in Hebrews where Jesus is seen as being perfect and without sin and in the Septuagint variously depicting human, and more occasionally divine, perfection.

Moses Maimonides’ Guide of the Perplexed is the greatest and most influential work in Jewish philosophy. It directly influenced Aquinas, Spinoza, and Leibniz, and the history of Jewish philosophy takes a decisive turn after the appearance of the Guide, in the wake of its Hebrew translation. Aquinas refers to “Rabbi Moyses” when he develops his own theory of analogical predication, and Spinoza has Maimonides and the Guide squarely in focus in the Tractatus Theologico-Politicus, when he presents his own theory of biblical interpretation.