If, by “metaphysics,” we mean “the ultimate science of Being and knowing” (OED), then we might rightly conclude that it is a pretentious, ambitious, even audacious enterprise, so much so that with Kant we might question whether or not such knowledge is possible for us, at least as defined. I am not in the slightest here taking up the cause of the logical positivists, but perhaps we are well advised to think this pursuit beyond our range, like firing a pistol at the moon, or hoping to catch a glimpse of its dark side with a flashlight. Perhaps all that such immodest speculation yields is a mere word pattern drawing out the implications of such ideas, at least until they meet a wall, a philosophical cul de sac beyond which we cannot pass. This path might proceed inexorably to some dialectical opposites not reconcilable into a higher, or more basic, synthesis. We do not know; we cannot tell, at least until God tells.
The true relation of our ideas to ultimate reality is not something we can well discern unless Ultimate Reality Himself tells us about it. Until He does, we are constrained to making educated guesses. These (hopefully) logically derived guesses seem by necessity to proceed according to analogy. By that I mean that concepts drawn from, or based upon, one mode of our experience are made to stand for or to relate meaningfully to Ultimate Reality. In what way it does so we cannot say for certain, but we hope that it does. What precise analogy exists between us and It we do not know, though theories abound. Short of revelation, those theories seem unable to rise to the level of fact, to knowledge, to Ultimate Reality (whether capitalized or not). Is the transcendent accessible? If so, by what means, and how do you know?
It seems to me that we do not know, and perhaps cannot know, that Ultimate Reality is contained or properly expressed in our language and thoughts about it, even if our analogies, by chance, are apt. Their actual significance is possibly beyond our ken. That ought to humble us; it does not. We might be trafficking in little more or little else than the world pictures our stunted minds toss forth, and the notions we try logically to drawn from them. When we begin to talk about the world as it is, and about its fundamental basis, we ought to proceed cautiously. I know of few metaphysicians who do.
Let us suppose that natural revelation is a perfectly wonderful and accurate revelation of God and that by it He can be well and deeply known. Even so, it would not follow that natural theology is reliable or is to trusted. It does not follow because additional correct supposals also are required. We must suppose also (A) that the human mind is acute enough, all on its own, to decode the divine message of nature, and (B) that the human soul is pious enough to receive that message humbly, to act on it obediently, and not to suppress it, alter it, or exchange it for a lie. Those supposals are false.
We are not humble and teachable recipients of nature’s message. We do not bow reverently before the God thus revealed or receptively to the Truth which He is. Quite the opposite: We suppress the Truth and exchange Him for a lie. In light of the revelation of God in nature, we make new gods, false gods, mind-forged idols, because, as Calvin rightly observed, the human heart is an idol factory, and for its raw materials uses the revelation of God which, because He is the very content of revelation, is God Himself.
That is exactly what happened: God made Himself known through nature (Rom. 1: 19, 20). But, being unthankful and vain, while still thinking ourselves wise, our hearts became darkened (v. 21). By means of those dark, idol-making hearts, we transformed God into the image of humans, animals, and even less because we did not want to retain God in our knowledge (vv. 23, 28). God therefore gave us over to the wicked actions that accompany idolatry (vv. 26, 27), the litany of which is shocking and gross (vv. 28-31). Our idols are of various sorts. They range from the golden calf of the ancient Jews to the impersonal, inarticulate, mechanistic causes and movers of the Greeks. Whether they are human, animal or mechanistic in representation, and whether or not they embody some small portion of the Truth, they all are idols. They all argue against our skills at metaphysics. They all say that when it comes to “the ultimate science of Being and knowing,” we are worse than rank amateurs. We are its enemies.