For whence do Marcion and Manichæus receive the Gospel while they reject the Law? For the New Testament arose out of the Old, and bears witness to the Old; if then they reject this, how can they receive what proceeds from it? Thus Paul was an Apostle of the Gospel, 'which God promised afore by His prophets in the holy Scriptures:' and our Lord Himself said, 'ye search the Scriptures, for they are they which testify of Me.' How then shall they confess the Lord unless they first search the Scriptures which are written concerning Him? And the disciples say that they have found Him, 'of whom Moses and the Prophets did write.' And what is the Law to the Sadducees if they receive not the Prophets? For God who gave the Law, Himself promised in the Law that He would raise up Prophets also, so that the same is Lord both of the Law and of the Prophets, and he that denies the one must of necessity deny the other also. And again, what is the Old Testament to the Jews, unless they acknowledge the Lord whose coming was expected according to it? For had they believed the writings of Moses, they would have believed the words of the Lord; for He said, 'He wrote of Me.' Moreover, what are the Scriptures to him of Samosata, who denies the Word of God and His incarnate Presence, which is signified and declared both in the Old and New Testament? And of what use are the Scriptures to the Arians also, and why do they bring them forward, men who say that the Word of God is a creature, and like the Gentiles 'serve the creature more than' God 'the Creator?' Thus each of these heresies, in respect of the peculiar impiety of its invention, has nothing in common with the Scriptures. And their advocates are aware of this, that the Scriptures are very much, or rather altogether, opposed to the doctrines of every one of them; but for the sake of deceiving the more simple sort (such as are those of whom it is written in the Proverbs, 'The simple believes every word),' they pretend like their 'father the devil ' to study and to quote the language of Scripture, in order that they may appear by their words to have a right belief, and so may persuade their wretched followers to believe what is contrary to the Scriptures. Assuredly in every one of these heresies the devil has thus disguised himself, and has suggested to them words full of craftiness. The Lord spoke concerning them, that 'there shall arise false Christs and false prophets, so that they shall deceive many.' Accordingly the devil has come, speaking by each and saying, 'I am Christ, and the truth is with me;' and he has made them, one and all, to be liars like himself. And strange it is, that while all heresies are at variance with one another concerning the mischievous inventions which each has framed, they are united together only by the common purpose of lying. For they have one and the same father that has sown in them all the seeds, of falsehood. Wherefore the faithful Christian and true disciple of the Gospel, having grace to discern spiritual things, and having built the house of his faith upon a rock, stands continually firm and secure from their deceits. But the simple person, as I said before, that is not thoroughly grounded in knowledge, such an one, considering only the words that are spoken and not perceiving their meaning, is immediately drawn away by their wiles. Wherefore it is good and needful for us to pray that we may receive the gift of discerning spirits, so that every one may know, according to the precept of John, whom he ought to reject, and whom to receive as friends and of the same faith. Now one might write at great length concerning these things, if one desired to go into details respecting them; for the impiety and perverseness of heresies will appear to be manifold and various, and the craft of the deceivers to be very terrible. But since holy Scripture is of all things most sufficient for us, therefore recommending to those who desire to know more of these matters, to read the Divine word, I now hasten to set before you that which most claims attention, and for the sake of which principally I have written these things.
5. Attempt of Arians to substitute a Creed for the Nicene.
I heard during my sojourn in these parts (and they were true and orthodox brethren that informed me), that certain professors of Arian opinions had met together, and drawn a confession of faith to their own liking, and that they intend to send word to you, that you must either subscribe to what pleases them, or rather to what the devil has inspired them with, or in case of refusal must suffer banishment. They are indeed already beginning to molest the Bishops of these parts; and thereby are plainly manifesting their disposition. For inasmuch as they frame this document only for the purpose of inflicting banishment or other punishments, what does such conduct prove them to be, but enemies of the Christians, and friends of the devil and his angels? And especially since they spread abroad what they like contrary to the mind of that gracious Prince, our most religious Emperor Constantius. And this they do with great craftiness, and, as appears to me, chiefly with two ends in view; first, that by obtaining your subscriptions, they may seem to remove the evil repute that rests upon the name of Arius, and may escape notice themselves as if not professing his opinions; and again, that by putting forth these statements they may cast a shade over the Council of Nicæa, and the confession of faith which was then put forth against the Arian heresy. But this proceeding does but prove the more plainly their own maliciousness and heterodoxy. For had they believed aright, they would have been satisfied with the confession put forth at Nicæa by the whole Ecumenic Council; and had they considered themselves calumniated and falsely called Arians, they ought not to have been so eager to innovate upon what was written against Arius, lest what was directed against him might seem to be aimed at them also. This, however, is not the course they pursue, but they conduct the struggle in their own behalf, just as if they were Arius. Observe how entirely they disregard the truth, and how everything they say and do is for the sake of the Arian heresy. For in that they dare to question those sound definitions of the faith, and take upon themselves to produce others contrary to them, what else do they but accuse the Fathers, and stand up in defence of that heresy which they opposed and protested against? And what they now write proceeds not from any regard for the truth, as I said before, but rather they do it as in mockery and by an artifice, for the purpose of deceiving men; that by sending about their letters they may engage the ears of the people to listen to these notions, and so put off the time when they will be brought to trial; and that by concealing their impiety from observation, they may have room to extend their heresy, which, 'like a gangrene,' eats its way everywhere.
Source: Ad Episcopus Aegypti et Libyae (New Advent)