Basil Contra Eunomius 2.32

Let’s see what follows:

If someone were to base his investigation on created works, from them he would be led up to the substances, discovering the Son is something made by the Unbegotten, whereas the Paraclete is something made by the Only-Begotten. Convinced on this basis of the superiority of the Only-Begotten that their activities are different, he accepts their difference in substance as indisputably demonstrated.

First of all, how is it possible to reason back from create works to substance? This is something which I for my part fail to see. For things which have been made are indicative of power and wisdom and skill, but not of the substance itself. Furthermore, they do not even necessarily communicate the entire power of the creator, seeing that the artisan can at times not put his entire strength into his activities; rather, he frequently attenuates his exertions for the products of his art. But if he were to set his whole power into motion for his product, even in this case it would be his strength that could be measured by means of his products, not his substance that could be comprehended, whatever it may be.

If, because of the simplicity and in-compositeness of the divine nature, Eunomius were to posit that the substance is concurrent with the power, and if, because of the goodness that belongs to God, he were to say that the whole power of the Father has been set into motion for the begetting of the Son, and the whole power of the Only-Begotten for the constitution of the Holy Spirit, so that one may consider the power of the Only-Begotten simultaneously with his substance on the basis of the Spirit, , and comprehended the power of the Father and his substance on the basis of the Only-Begotten, note what the consequence of this is. The very points he uses to try to confirm the unlikeness of the substance actually confirm its likeness! For it the power has nothing in common with the substance, how could he be led from the created works, which are the effects of power, to the comprehension of the substance? But if the power and substance are the same thing, then that which characterises the power will also completely characterise the substance. Hence the created works will not bring one to the unlikeness of substance, as you say, but rather to the exactness of the likeness. So once again, this attempt confirms our account rather than his.

Either there is no basis on which to demonstrate his claims, or, if he were to draw his images from human affairs, he would discover that it is not from the products of the artisan that we comprehend the artisan’s substance, but that it is from that which has been begotten that we come to know the nature of the begetter. After all, it is impossible to comprehend the substance of the house-builder from the house. But on the basis of that which is begotten it is easy to conceive of the nature of the begetter. Consequently, if the Only-Begotten is a created work, he does not communicate to us of the substance of the Father. But if he makes the Father known to us through himself, he is not a created work but rather the true Son, “the image of God,” [2Cor. 4.4], and “the character of His subsistance,” [Col. 1.15]. So much for this subject.