It will not do to apply this conception, as drawn out above, of the Father and Son to the Creation, as they insist on doing: but we must contemplate the Son apart with the Father, and believethat the Creation had its origin from a definite point
We have shown, then, by what we have said that the Only-begotten and the Holy Spirit are not to be looked for in the creation but are to be believed above it; and that while the creation may perhaps by the persevering efforts of ambitious seekers be seized in its own beginning, whatever that may be, the supernatural will not the more for that come within the realm of knowledge, for no mark before the ages indicative of its nature can be found. Well, then, if in this uncreate existence those wondrous realities, with their wondrous names of Father, Son, and Holy Ghost, are to be in our thoughts, how can we imagine, of that pre-temporal world, that which our busy, restless minds perceive in things here below by comparing one of them with another and giving it precedence by an interval of time? For there, with the Father, unoriginate, ungenerate, always Father, the idea of the Son as coming from Him yet side by side with Him is inseparably joined; and through the Son and yet with Him, before any vague and unsubstantial conception comes in between, the Holy Spirit is found at once in closest union; not subsequent in existence to the Son, as if the Son could be thought of as ever having been without the Spirit; but Himself also owning the same cause of His being, i.e. the God over all, as the Only-begotten Light, and having shone forth in that very Light, being divisible neither by duration nor by an alien nature from the Father or from the Only-begotten. There are no intervals in that pre-temporal world: and difference on the score of being there is none. It is not even possible, comparing the uncreate with the uncreated, to see differences; and the Holy Ghost is uncreate, as we have before shown.
This being the view held by all who accept in its simplicity the undiluted Gospel, what occasion was there for endeavouring to dissolve this fast union of the Son with the Father by means of the creation, as if it were necessary to suppose either that the Son was from everlasting along with the creation, or that He too, equally with it, was later? For the generation of the Son does not fall within time, any more than the creation was before time: so that it can in no kind of way be right to partition the indivisible, and to insert, by declaring that there was a time when the Author of all existence was not, this false idea of time into the creative Source of the Universe.
Our previous contention, therefore, is true, that the everlastingness of the Son is included, along with the idea of His birth, in the Father's ungeneracy; and that, if any interval were to be imagined dividing the two, that same interval would fix a beginning for the life of the Almighty;— a monstrous supposition. But there is nothing to prevent the creation, being, as it is, in its own nature something other than its Creator and in no point trenching on that pure pre-temporal world, from having, in our belief, a beginning of its own, as we have said. To say that the heavens and the earth and other contents of creation were out of things which are not, or, as the Apostle says, out of “things not seen,” inflicts no dishonour upon the Maker of this universe; for we know from Scripture that all these things are not from everlasting nor will remain for ever. If on the other hand it could be believed that there is something in the Holy Trinity which does not coexist with the Father, if following out this heresy any thought could be entertained of stripping the Almighty of the glory of the Son and Holy Ghost, it would end in nothing else than in a God manifestly removed from every deed and thought that was good and godlike. But if the Father, existing before the ages, is always in glory, and the pre-temporal Son is His glory, and if in like manner the Spirit of Christ is the Son's glory, always to be contemplated along with the Father and the Son, what training could have led this man of learning to declare that there is a 'before' in what is timeless, and a 'more honourable' in what is all essentially honourable, and preferring, by comparisons, the one to the other, to dishonour the latter by this partiality? The term in opposition to the more honourable makes it clearer still whither he is tending.
Source: Against Eunomius (New Advent)