4th–15th centuries

Trinitarian monotheism in the face of Judaism and Islam

Already Gregory of Nyssa presented the Trinity as a middle way: from the Jewish conception the unity of nature remains, from Hellenism the distinction of hypostases. In the 7th–11th centuries the Jewish side objected to the Trinity, the icons and the cross, and Christians replied by appealing to the "Shema", to "let us make man" and to the claim that Abraham already knew the Trinity. The rise of Islam, according to Pelikan, posed a new challenge to Byzantine theology for which it was poorly prepared: the main points of divergence were the unity of God and the prophethood of Muhammad. Christians replied that the three hypostases have one substance and are not three gods, and that the Father is the single principle of the Son and the Spirit; the apology for the Trinity took a central place in anti-Muslim treatises.