He does wrong in making the being of the Father alone proper and supreme, implying by his omission of the Son and the Spirit that theirs is improperly spoken of, and is inferior
I think that from what has been said it will be clear what is the aim of these newly-devised names. He drops them as the base of operations or foundation-stone of all this work of mischief to the Faith: once he can get the idea into currency that the one Being alone is supreme and proper in the highest degree, he can then assail the other two, as belonging to the inferior and not regarded as properly Being. He shows this especially in what follows, where he is discussing the belief in the Son and the Holy Spirit, and does not proceed with these names, so as to avoid bringing before us the proper characteristic of their nature by means of those appellations: they are passed over unnoticed by this man who is always telling us that minds of the hearers are to be directed by the use of appropriate names and phrases.
Yet what name could be more appropriate than that which has been given by the Very Truth? He sets his views against the Gospel, and names not the Son, but 'a Being existing through the First, but after It though before all others.' That this is said to destroy the right faith in the Only-begotten will be made plainer still by his subsequent arguments. Still there is only a moderate amount of mischief in these words: one intending no impiety at all towards Christ might sometimes use them: we will therefore omit at present all discussion about our Lord, and reserve our reply to the more open blasphemies against Him.
But on the subject of the Holy Spirit the blasphemy is plain and unconcealed: he says that He is not to be ranked with the Father or the Son, but is subject to both. I will therefore examine as closely as possible this statement.
Source: Against Eunomius (New Advent)