Several ways of controverting his quibbling syllogisms
If, then, all that is the Father's is in the Only-begotten, and He is in the Father, and the Fatherhood is not dissociated from the 'not having been generated,' I for my part cannot see what there is to think of in connection with the Father, by Himself, that is parted by any interval so as to precede our apprehension of the Son. Therefore we may boldly encounter the difficulties started in that quibbling syllogism; we may despise it as a mere scare to frighten children, and still assert that God is Holy, and Immortal, and Father, and Ungenerate, and Everlasting, and everything all at once; and that, if it could be supposed possible that you could withhold one of these attributes which devotion assigns to Him, all would be destroyed along with that one. Nothing, therefore, in Him is older or younger; else He would be found to be older or younger than Himself. If God is not all His attributes always, but something in Him is, and something else only becoming, following some order of sequence (we must remember God is not a compound; whatever He is is the whole of Him), and if according to this heresy He is first Ungenerate and afterwards becomes Father, then, seeing that we cannot think of Him in connection with a heaping together of qualities, there is no alternative but that the whole of Him must be both older and younger than the whole of Him, the former by virtue of His Ungeneracy, the latter by virtue of His Fatherhood. But if, as the prophet says of God, He “is the same,” it is idle to say that before He begot He was not Himself Ungenerate; we cannot find either of these names, the Father and the Ungenerate One, parted from the other; the two ideas rise together, suggested by each other, in the thoughts of the devout reasoner. God is Father from everlasting, and everlasting Father, and every other term that devotion assigns to Him is given in a like sense, the mensuration and the flow of time having no place, as we have said, in the Eternal.
Let us now see the remaining results of his expertness in dealing with words; results, which he himself truly says, are at once ridiculous and lamentable. Truly one must laugh outright at what he says, if a deep lament for the error that steeps his soul were not more fitting. Whereas Father, as we teach, includes, according to one of its meanings, the idea of the Ungenerate, he transfers the full signification of the word Father to that of the Ungenerate, and declares “If Father is the same as Ungenerate, it is allowable for us to drop it, and use Ungenerate instead; thus, the Ungenerate of the Son is Ungenerate; for as the Ungenerate is Father of the Son, so reversely the Father is Ungenerate of the Son.” After this a feeling of admiration for our friend's adroitness steals over me, with the conviction that the many-sided subtlety of his theological training is quite beyond the capacity of most. What our Teacher said was embraced in one short sentence, to the effect that it was possible that by the title 'Father' the Ungeneracy could be signified; but Eunomius' words depend for their number not on the variety of the thoughts, but on the way that anything within the circuit of similar names can be turned about. As the cattle that run blindfold round to turn the mill remain with all their travel in the same spot, so does he go round and round the same topic, and never leaves it. Once he said, ridiculing us, that 'Father' does not signify the having begotten, but the being from nothing. Again he wove a similar dilemma, “If Father signifies Ungeneracy, before He begot He was not ungenerate.” Then a third time he resorts to the same trick. “It is allowable for us to drop Father, and to use Ungenerate instead;” and then directly he repeats the logic so often vomited. “For as the Ungenerate is Father of the Son, so reversely the Father is Ungenerate of the Son.” How often he returns to his vomit; how often he blurts it out again! Shall we not, then, annoy most people, if we drag about our argument in company with this foolish display of words? It would be perhaps more decent to be silent in a case like this; still, lest any one should think that we decline discussion because we are weak in pleas, we will answer thus to what he has said. 'You have no authority, Eunomius, for calling the Father the Ungenerate of the Son, even though the title Father does signify that the Begetter was from no cause Himself. For as, to take the example already cited, when we hear the word 'Emperor' we understand two things, both that the one who is pre-eminent in authority is subject to none, and also that he controls his inferiors, so the title Father supplies us with two ideas about the Deity, one relating to His Son, the other to His being dependent on no preconceivable cause. As, then, in the case of 'Emperor' we cannot say that because the two things are signified by that term, viz., the ruling over subjects and the not having any to take precedence of him, there is any justification for speaking of the 'Unruled of subjects,' instead of the 'Ruler of the nation,' or allowing so much, that we may use such a juxtaposition of words, in imitation of king of a nation, as kingless of a nation, in the same way when 'Father' indicates a Son, and also represents the idea of the Ungenerate, we may not unduly transfer this latter meaning, so as to attach this idea of the Ungenerate fast to a paternal relationship, and absurdly say 'the Ungenerate is Ungenerate of the Son.'
He treads on the ground of truth, he thinks, after such utterances; he has exposed the absurdity of his adversaries' position; how boastfully he cries, “And what sane thinker, pray, ever yet wanted the natural thought to be suppressed, and welcomed the paradoxical?” No sane thinker, most accomplished sir; and therefore our argument neither, which teaches that while the term Ungenerate does suit our thoughts, and we ought to guard it in our hearts intact, yet the term Father is an adequate substitute for the one which you have perverted, and leads the mind in that direction. Remember the words which you yourself quoted; Basil did not 'want the natural thought to be suppressed, and welcome the paradoxical,' as you phrase it; but he advised us to avoid all danger by suppressing the mere word Ungenerate, that is, the expression in so many syllables, as one which had been evilly interpreted, and besides was not to be found in Scripture; as for its meaning he declares that it does most completely suit our thoughts.
Source: Against Eunomius (New Advent)