Basil Contra Eunomius 1.12

Generally speaking, how much arrogance and pride would it take for someone to think that he had discovered the very substance of God above all? For by their bragging they nearly eclipse even the one who said, Above the stars I will set my throne (Isaiah 14.13). Yet these men are not insolently attacking the stars or heaven, but are bragging that they have penetrated the very substance of the God of the universe! Let’s ask him from which source he claims to have comprehended it. So, then, from a common notion? But this tells us that God exists, not what God is. Perhaps from the Spirit’s teaching? Which one? Where is it located? Isn’t it clear that the great David, to whom God manifested the secret and hidden things of his own wisdom, confessed that such knowledge is inaccessible? For he said: I regard knowledge of you as a marvel, as too strong—I am not able to attain it (Ps. 138.6). And when Isaiah came to contemplate the glory of God, what did he reveal to us about the divine substance? He is the one who testified in the prophecy about Christ, saying: Who shall tell of his begetting? (Is. 53.8). Then there’s Paul,  the vessel of election (Acts 9.15), who had Christ speaking in him (2Cor 13.3) and  was snatched away up to the third heaven and heard ineffable words which are impossible for a person to utter (2Cor 12.2-4). What teaching did he bequeath to us about the substance of God? He is the one who peered into the particular reasons for the economy and cried out with this voice, as if the vastness of what he contemplated made him dizzy: O the depths of the riches and wisdom and knowledge of God! How inscrutable are his judgments, and how unsearchable are his ways! (Rom. 11.33) If these things are beyond the understanding of those who have attained the measure of the knowledge of Paul, how great is the conceit of those who profess to know the substance of God.

I would like to ask them about the earth upon which they stand from which they come—what do they say? What do they tell us is its substance? If they were to argue incontrovertibly about what lies on the ground and under their feet, we would believe them when they concern themselves with the things beyond every motion. What, then, is the substance of the earth? What is its mode of comprehension? Let them respond and tell us whether it is a rational account or sense-perception, by which of the sense is it comprehensible? By sight? But sight apprehends colours. Perhaps by touch? But touch can distinguish between hardness and softness, between hot and cold, and such things, none of which anyone would call substance—unless he had been carried away to the utmost insanity! For taste and smell, what do we need to say about these senses? The former apprehends flavours; the latter odours. And as for hearing, it is perceptive of noises and voices, things which have no relationship to the earth. Therefore, the only option left to them is to say that they have discovered the substance of the earth by a rational account. What sort of rational account is this? Where is it located in the Scriptures? Which of the saints handed it down?