11, 12. Marcellus and his disciples, like Arians, say that the Word was, not indeed created, but issued, to create us, as if the Divine silence were a state of inaction, and when God spoke by the Word, He acted; or that there was a going forth and return of the Word; a doctrine which implies change and imperfection in Father and Son.
11 They fall into the same folly with the Arians; for Arians also say that He was created for us, that He might create us, as if God waited till our creation for His issue, as the one party say, or His creation, as the other. Arians then are more bountiful to us than to the Son; for they say, not we for His sake, but He for ours, came to be; that is, if He was therefore created, and subsisted, that God through Him might create us. And these, as irreligious or more so, give to God less than to us. For we oftentimes, even when silent, yet are active in thinking, so as to form the results of our thoughts into images; but God they would have inactive when silent, and when He speaks then to exert strength; if, that is, when silent He could not make, and when speaking He began to create. For it is just to ask them, whether the Word, when He was in God, was perfect, so as to be able to make. If on the one hand He was imperfect, when in God, but by being begotten became perfect, we are the cause of His perfection, that is, if He has been begotten for us; for on our behalf He has received the power of making. But if He was perfect in God, so as to be able to make, His generation is superfluous; for He, even when in the Father, could frame the world; so that either He has not been begotten, or He was begotten, not for us, but because He is ever from the Father. For His generation evidences, not that we were created, but that He is from God; for He was even before our creation.
12. And the same presumption will be proved against them concerning the Father; for if, when silent, He could not make, of necessity He has gained power by begetting, that is, by speaking. And whence has He gained it? And wherefore? If, when He had the Word within Him, He could make, He begets needlessly, being able to make even in silence. Next, if the Word was in God before He was begotten, then being begotten He is without and external to Him. But if so, how says He now, 'I in the Father and the Father in Me?' but if He is now in the Father, then always was He in the Father, as He is now, and needless is it to say, 'For us was He begotten, and He reverts after we are formed, that He may be as He was.' For He was not anything which He is not now, nor is He what He was not; but He is as He ever was, and in the same state and in the same respects; otherwise He will seem to be imperfect and alterable. For if, what He was, that He shall be afterwards, as if now He were not so, it is plain, He is not now what He was and shall be. I mean, if He was before in God, and afterwards shall be again, it follows that now the Word is not in God. But the Lord refutes such persons when He says, 'I in the Father and the Father in Me;' for so is He now as He ever was. But if so He now is, as He was ever, it follows, not that at one time He was begotten and not at another, nor that once there was silence with God, and then He spoke, but there is ever a Father, and a Son who is His Word, not in name alone a Word, nor the Word in notion only a Son, but existing coessential with the Father, not begotten for us, for we are brought into being for Him. For, if He were begotten for us, and in His begetting we were created, and in His generation the creature consists, and then He returns that He may be what He was before, first, He that was begotten will be again not begotten. For if His progression be generation, His return will be the close of that generation, for when He has come to be in God, God will be silent again. But if He shall be silent, there will be what there was when He was silent, stillness and not creation, for the creation will cease to be. For, as on the Word's outgoing, the creation came to be, and existed, so on the Word's retiring, the creation will not exist. What use then for it to come into being, if it is to cease? Or why did God speak, that then He should be silent? And why did He issue One whom He recalls? And why did He beget One whose generation He willed to cease? Again it is uncertain what He shall be. For either He will ever be silent, or He will again beget, and will devise a different creation (for He will not make the same, else that which was made would have remained, but another); and in due course He will bring that also to a close, and will devise another, and so on without end.
Source: Four Discourses Against the Arians (New Advent)