He then shows the unity of the Son with the Father and Eunomius' lack of understanding and knowledgein the Scriptures
What he adds next after this is as follows:— “Having no sharer,” he says, “in His Godhead, no divider of His glory, none who has lot in His power, or part in His royal throne: for He is the one and only God, the Almighty, God of Gods, King of Kings, Lord of Lords.” I know not to whom Eunomius refers when he protests that the Father admits none to share His Godhead with Himself. For if he uses such expressions with reference to vain idols and to the erroneous conceptions of those who worship them (even as Paul assures us that there is no agreement between Christ and Belial, and no fellowship between the temple of God and idols) we agree with him. But if by these assertions he means to sever the Only-begotten God from the Godhead of the Father, let him be informed that he is providing us with a dilemma that may be turned against himself to refute his own impiety. For either he denies the Only-begotten God to be God at all, that he may preserve for the Father those prerogatives of deity which (according to him) are incapable of being shared with the Son, and thus is convicted as a transgressor by denying the God Whom Christians worship, or if he were to grant that the Son also is God, yet not agreeing in nature with the true God, he would be necessarily obliged to acknowledge that he maintains Gods sundered from one another by the difference of their natures. Let him choose which of these he will—either to deny the Godhead of the Son, or to introduce into his creed a plurality of Gods. For whichever of these he chooses, it is all one as regards impiety: for we who are initiated into the mystery of godliness by the Divinely inspired words of the Scripture do not see between the Father and the Son a partnership of Godhead, but unity, inasmuch as the Lord has taught us this by His own words, when He says, “I and the Father are one,” and “he that has seen Me has seen the Father.” For if He were not of the same nature as the Father, how could He either have had in Himself that which was different? Or how could He have shown in Himself that which was unlike, if the foreign and alien nature did not receive the stamp of that which was of a different kind from itself? But he says, “nor has He a divider of His glory.” Herein he speaks in accordance with the fact, even though he does not know what he is saying: for the Son does not divide the glory with the Father, but has the glory of the Father in its entirety, even as the Father has all the glory of the Son. For thus He spoke to the Father “All Mine are Yours and Yours are Mine.” Wherefore also He says that He will appear on the Judgment Day “in the glory of the Father,” when He will render to every man according to his works. And by this phrase He shows the unity of nature that subsists between them. For as “there is one glory of the sun and another glory of the moon,” because of the difference between the natures of those luminaries (since if both had the same glory there would not be deemed to be any difference in their nature), so He Who foretold of Himself that He would appear in the glory of the Father indicated by the identity of glory their community of nature.
But to say that the Son has no part in His Father's royal throne argues an extraordinary amount of research into the oracles of God on the part of Eunomius, who, after his extreme devotion to the inspired Scriptures, has not yet heard, “Seek those things which are above, where Christ sits on the right hand of God,” and many similar passages, of which it would not be easy to reckon up the number, but which Eunomius has never learned, and so denies that the Son is enthroned together with the Father. Again the phrase, “not having lot in his power,” we should rather pass by as unmeaning than confute as ungodly. For what sense is attached to the term “having lot” is not easy to discover from the common use of the word. Those cast lots, as the Scripture tells us, for the Lord's vesture, who were unwilling to rend His garment, but disposed to make it over to that one of their number in whose favour the lot should decide. They then who thus cast lots among themselves for the “coat” may be said, perhaps, to “have had lot” in it. But here in the case of the Father, the Son, and the Holy Ghost, inasmuch as Their power resides in Their nature (for the Holy Spirit breathes “where He lists,” and “works all in all as He will,” and the Son, by Whom all things were made, visible and invisible, in heaven and in earth, “did all things whatsoever He pleased,” and “quickens whom He will,” and the Father put “the times in His own power,” while from the mention of “times” we conclude that all things done in time are subject to the power of the Father), if, I say, it has been demonstrated that the Father, the Son, and the Holy Spirit alike are in a position of power to do what They will, it is impossible to see what sense there can be in the phrase “having lot in His power.” For the heir of all things, the maker of the ages, He Who shines with the Father's glory and expresses in Himself the Father's person, has all things that the Father Himself has, and is possessor of all His power, not that the right is transferred from the Father to the Son, but that it at once remains in the Father and resides in the Son. For He Who is in the Father is manifestly in the Father with all His own might, and He Who has the Father in Himself includes all the power and might of the Father. For He has in Himself all the Father, and not merely a part of Him: and He Who has Him entirely assuredly has His power as well. With what meaning, then, Eunomius asserts that the Father has “none who has lot in His power,” those perhaps can tell who are disciples of his folly: one who knows how to appreciate language confesses that he cannot understand phrases divorced from meaning. The Father, he says, “has none Who has lot in His power.” Why, who is there that says that the Father and Son contend together for power and cast lots to decide the matter? But the holy Eunomius comes as mediator between them and by a friendly agreement without lot assigns to the Father the superiority in power.
Source: Against Eunomius (New Advent)