Knowledge of God and its bases has never been an uncontested thing in theological development and discourse. The Apostle Paul, of course, famously addresses the issue of knowledge of God in Romans 1 which has become the locus classicus for proponents of an ostensible natural theology:

¹⁸ For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men who suppress the truth in unrighteousness, ¹⁹ because that which is known about God is evident within them; for God made it evident to them. ²⁰ For since the creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen, being understood through what has been made, so that they are without excuse. ²¹ For even though they knew God, they did not honor Him as God or give thanks, but they became futile in their speculations, and their foolish heart was darkened. ²² Professing to be wise, they became fools, ²³ and exchanged the glory of the incorruptible God for an image in the form of corruptible man and of birds and four-footed animals and crawling creatures.

To appropriate this text as if it just does teach a natural theology, or way of thinking God in a form like Thomas Aquinas’ analogia entis entails—which would be a subset of a natural theology simpliciter—isn’t justified. Those who would simply assert such need to present an argument that Paul is intending to teach that who and what God is, is latent within something like the vestiges of creation.

On a different basis, but as corollary with something like Aquinas’ analogia entis, Rene Descartes attempts to present a certain knowledge of God from his methodological skepticism; thus, doubting everything as a basis for knowing until he gets to himself (so his cogito ergo sum). Descartes is offering his own form of an analogia entis, thinking godness from his idea of God that he has more certainly established by conniving God an epistemic ground founded in his own thinking as a prius to God.

Martin Luther yells a resounding Nein (as does Karl Barth in his own way). Eberhard Jüngel presents an insightful commentary on how Luther differs from Descartes on a theory for a knowledge of God. He writes:

Remaining at the level of rational knowledge of God, for Luther too there is a fundamental cognitive difference between the “that-being” and “what-being” of God, between the ‘existence’ and the ‘essence’ of God: There is “a vast difference between knowing that there is a God and knowing who or what God is.” See Luther, Lectures on the Minor Prophets II: Jonah, Habakkuk (in Luther’s Works, vol. 19), ed. Hilton C. Oswald (St. Louis: Concordia Publishing House, 1974), p. 55. Whereas Descartes begins with the ‘essence of God’ which is comprehended in the ‘idea of God’ and moves to the ascertainment of the ‘existence of God’ through the ego . . . , Luther takes another route: “Reason . . . knows that there is a God, but it does not know who or which is the true God.. . .” And it is the misfortune of reason overstepping its boundaries that it wants to move from the knowledge that there is a God somehow to the knowledge of who God is, as Luther says: “Thus reason also plays blindman’s buff with God; it consistently gropes in the dark and misses the mark. It calls that God which is not God and fails to call Him God who really is God. Reason would do neither the one nor the other if it were not conscious of the existence of God or if it really knew who and what God is. Therefore it rushes in clumsily an assigns the name God and ascribes the divine honor to its own idea of God. Thus reason never finds the true God, but knows the former [scil. that God exists]—it is inscribed in everybody’s heart; the latter is taught only by the Holy Spirit.. . .” This difference does not obtain for faith. For faith knows that God is in that it experiences who or what God is.[1]

Luther concedes that natural humans have an abstract notion of Godness, but this is where such knowledge of God terminates. Ultimately, it could be inferred, that if this was the basis for a knowledge of God in conclusion, what people would end up with, in regard to filling out this abstract knowledge of Godness, would end up being merely a self-projection of the self onto this ‘natural’ schematizing towards a knowledge of God. For Luther, as Juengel helpfully distills, a genuine knowledge of God is only one that is grounded in the eye of faith. Which if this is the case, and I think it is, presupposes that first the hidden God (Deus absconditus) must come down to us and be with as and be the revealed God (Deus revelatus) for us. This is nothing short of what Barth (and TF Torrance) pick up on, and develop into, in Barth’s case, what he identifies as an analogia fidei/relationis (‘analogy of faith/relation’). But sticking with Luther contra Descartes, per Juengel, reason is incapable of knowing who and then what God is. And we could surmise from this if natural reason is incapable in precisely this way, then constructing a theology proper based upon categories provided for by the [classical] philosophers, like Plato and Aristotle represent, ends up being fool’s errand—a fool’s errand because this method can only lead the seeker of God into an abyss of idolatry (as Ludwig Feuerbach understood so presciently in his own modern context).

On a negative note, I present this to you so that you can more critically read what certain evangelical, Reformed and Lutheran theologians are attempting to recover in the name of an orthodox doctrine of God. They are recovering notional categories for thinking God from the direct heirs, in both the “orthodox” realms of Reformed and Lutheran thinkers, to Thomas Aquinas; and we might add, tangled into this, something like Descartes’ thinking in regard to a certainty towards knowing God. I would strongly recommend to avoid this approach in attempting to think rightly, and thus orthodoxly about the living God. As Luther knew, such intellectualist machinations about God, again, can only finally terminate in a conception of godness that is only able to repose in the notion that some ‘unknown god,’ an abstraction of the human-knower, must certainly exist. And if this ‘ratiocination’ about God is followed, what is left, is for said rationales to say both what and who God is; with an emphasis on the former, as we see fruiting in both Descartes and Thomas.

On a positive note, take heart, for those who seek to know God, as Luther so brightly understood, from the faith of Christ, it is here where the seeker stands on solid ground; as the Apostle has written: “For no man can lay a foundation other than the one which is laid, which is Jesus Christ.” When the Christian builds upon this foundation, the one seen with the faith of Christ, it is thence that the knower of God can genuinely be called such. When we aren’t building cathedrals of knowledge of God that wait upon ‘revelation perfecting reason,’ and instead allow God’s Self-revelation to impose Himself upon us, afresh anew by the Holy Spirit in Christ, it is here that the Christian can confidently proclaim that they see the face (prosopon) of God in Jesus Christ. This is the foundation, God’s being-in-becoming for the world in Jesus Christ that God has freely elected as the basis for the would-be knower of God to genuinely know who (and thus what) He is. And this is the all-important conclusion: that God is the one who has laid the foundation for knowing God in and from Himself, for us in Jesus Christ. He hasn’t left the Christian to be an orphan, or archaeologist attempting to discover God under the rubble of the artifacts of paleo pagan thinkers of a purported ultimacy. No, God has deigned that we know God from God alone in Christ alone by grace alone through faith alone; indeed, the faith of Christ.

I won’t directly address the Romans 1 passage, per se. I will leave that to the reader, and see if they can infer how I “exegeted” that pericope throughout the body of this post. (I have also written other posts that deal directly with that passage vis-à-vis a purported natural theology reading)

[1] Eberhard Jüngel, God as the Mystery of the World, trans. by Darrell L. Guder (Eugene, OR: Wipf&Stock, 1983), 124 n. 53.