23. The fourth book starts with the doctrines of the heretics, and disowns complicity in the fallacies whereby they are traducing the faith of the Church. It publishes that infidel creed which a number of them have lately promulgated The letter of Arius to Alexander; Book iv., §§ 12, 13., and exposes the dishonesty, and therefore the wickedness, of their arguments from the Law for what they call the unity of God. It sets out the whole evidence of Law and Prophets to demonstrate the impiety of asserting the unity of God to the exclusion of the Godhead of Christ, and the treason of alleging that if Christ be God the Only-begotten, then God is not one.