56. This discipline, then, which is the medicine of the mind, as far as we can gather from the sacred Scriptures, includes two things, restraint and instruction. Restraint implies fear, and instruction love, in the person benefited by the discipline; for in the giver of the benefit there is the love without the fear. In both of these God Himself, by whose goodness and mercy it is that we are anything, has given us in the two Testaments a rule of discipline. For though both are found in both Testaments, still fear is prominent in the Old, and love in the New; which the apostle calls bondage in the one, and liberty in the other. Of the marvellous order and divine harmony of these Testaments it would take long to speak, and many pious and learned men have discoursed on it. The theme demands many books to set it forth and explain it as far as is possible for man. He, then, who loves his neighbor endeavors all he can to procure his safety in body and in soul, making the health of the mind the standard in his treatment of the body. And as regards the mind, his endeavors are in this order, that he should first fear and then love God. This is true excellence of conduct, and thus the knowledge of the truth is acquired which we are ever in the pursuit of.
57. The Manichæans agree with me as regards the duty of loving God and our neighbor, but they deny that this is taught in the Old Testament. How greatly they err in this is, I think, clearly shown by the passages quoted above on both these duties. But, in a single word, and one which only stark madness can oppose, do they not see the unreasonableness of denying that these very two precepts which they commend are quoted by the Lord in the Gospel from the Old Testament, "Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind;" and the other, "Thou shalt love thy neighbor as thyself?"  Or if they dare not deny this, from the light of truth being too strong for them, let them deny that these precepts are salutary; let them deny, if they can, that they teach the best morality; let them assert that it is not a duty to love God, or to love our neighbor; that all things do not issue in good to them that love God; that it is not true that the love of our neighbor worketh no ill (a two-fold regulation of human life which is most salutary and excellent). By such assertions they cut themselves off not only from Christians, but from mankind. But if they dare not speak thus, but must confess the divinity of the precepts, why do they not desist from assailing and maligning with horrible profanity the books from which they are quoted?
58. Will they say, as they often do, that although we find these precepts in the books, it does not follow that all is good that is found there? How to meet and refute this quibble I do not well see. Shall I discuss the words of the Old Testament one by one, to prove to stubborn and ignorant men their perfect agreement with the New Testament? But when will this be done? When shall I have time, or they patience? What, then, is to be done? Shall I desert the cause, and leave them to escape detection in an opinion which, though false and impious, is hard to disprove? I will not. God will Himself be at hand to aid me; nor will He suffer me in those straits to remain helpless or forsaken.