Aquinas vs. Kant: Renewing Your Mind

Added: 2026-06-03

[00:00:00]18th century philosopher Immanuel Kant questioned whether we could know anything about God, and many theologians of his era said things like this.

[00:00:09]>> You can maybe assume the existence of God, presuppose the existence of God, or grant the existence of God by faith, but what you cannot do is prove the existence of God by rational categories.

[00:00:25]>> [music] >> Many theologians, however, refused to buy Kant's argument. They looked back at men like Thomas Aquinas, who asserted that God's existence could indeed be proven.

[00:00:40]Hello and welcome to the Wednesday edition of Renewing Your Mind, and let's dive into this debate. Here's R.C.

[00:00:46]Sproul from his series Defending Your Faith.

[00:00:52]>> Saint Thomas Aquinas, who is called the Doctor Angelicus or the Angelic Doctor of the Roman Catholic Church, was a titan in the realm of philosophy and theology in the Middle Ages.

[00:01:06]And he is most responsible for constructing what is known in the history of theoretical thought as the classical synthesis.

[00:01:17]That is by showing that philosophy, as well as theology, manifested the truth of the existence of God. And so strong was this synthesis that it was rare in those days for intellectuals to challenge the notion of the existence of God. And historically, the principal arguments for the existence of God were the following. First of all, there was the famous ontological argument for the existence of God, which we'll look at later, which had been formulated early on by Augustine in his version, but made most famous by the version set forth by Saint Anselm of Canterbury.

[00:02:11]And the ontological argument for the existence of God was an argument for God from being.

[00:02:19]And as I say, I'll take time later to explain more of that for you.

[00:02:24]Secondly, there was the cosmological argument. And the cosmological argument was that argument that reasoned from the world or the cosmos back to the origin of the world to the creator. It was the argument based on the law of causality, arguing that that world that we perceive has to have a transcendent cause.

[00:02:56]And so the cosmological argument was part of that historical tradition. Then there was also what was called the teleological argument.

[00:03:07]That word teleological may be foreign to some. It comes from the Greek word telos, which is the Greek word that means end or purpose or goal.

[00:03:24]The teleological argument was the argument from design.

[00:03:31]That is the presence of design in the universe would indicate a designer.

[00:03:40]And the argument that was teleological said that all around nature we see things operating in a logical way, and that they are put together with an amazing symmetry that suggests an intelligent creator or an intelligent designer.

[00:04:04]And so, the argument from the appearance of purpose and order and harmony in the universe was used to argue for the existence of God. And in addition to that, there was the moral argument for God, which I'll pass over for now.

[00:04:22]But, these arguments, as they had been articulated by Christian philosophers through the centuries, represented formidable proofs for the existence of God and made it possible for Christianity to dominate in the academic world, particularly in Western Europe, where in the University of the Middle Ages, theology was seen as the queen of the sciences and philosophy her handmaiden.

[00:04:59]That is, the science of philosophy operated as a servant for the aims and goals of theology because it was seen that there was a unity between theological affirmations and philosophical thinking and evidence. So, again, we want to put to rest the idea that Saint Thomas Aquinas was trying to separate philosophy from theology or nature from grace, but was trying to maintain their unity in putting together the classical synthesis that reigned for so many centuries.

[00:05:40]And this synthesis enjoyed dominance in theoretical thought until the massive work of Immanuel Kant that took place towards the end of the 18th century.

[00:05:59]In the history of Western thought, we see the publication of Immanuel Kant's book the Critique of Pure Reason as a watershed moment in history.

[00:06:14]It was a book that was revolutionary in scope.

[00:06:21]In fact, its timing was almost exactly at the same time as the American Revolution.

[00:06:30]And we tend to think of the American Revolution as one of the most significant events to take place in modern history.

[00:06:40]And that the American Revolution changed the course of world history forever.

[00:06:46]And yet at the same time, I would say that the intellectual revolution that was provoked by Kant's Critique of Pure Reason was even more far-reaching in terms of its revolutionary impact than anything that was accomplished in the political arena by the American colonies in their revolt against the crown of England.

[00:07:12]In his famous Critique of Pure Reason, Kant, who had been awakened by the skepticism of the British empiricist David Hume, said he was awakened from his dogmatic slumbers and was afraid that Hume's critique of causality would sow the seeds of destruction for all of science, not to mention religion and faith.

[00:07:42]And so, part of what was motivating Kant in his critique was to rescue science from scepticism.

[00:07:56]And along the way, he laid his axe at the root of the tree of the classical synthesis, giving a comprehensive critique of the traditional arguments for the existence of God.

[00:08:10]And with that, Kant was not an atheist and was not trying to be totally destructive of Christianity, but rather he was trying to attack reason in order to make room for faith.

[00:08:25]Because he saw Christianity having degenerated into too much of a dependence on human reason and not enough on faith. And so, he gave this critique of the existence of God. Now, at the heart of this critique, I shouldn't say he gave a critique of the existence of God. That's incorrect.

[00:08:48]He gave a critique of the arguments for the existence of God. He himself affirmed the existence of God, but he said that you cannot know the existence of God from natural reason.

[00:09:02]His was an attack against natural theology.

[00:09:08]And he said that there were two realms, as it were, the realm of what he called the noumenal realm, or the noumenal world, and down here, the phenomenal realm.

[00:09:27]And in the noumenal realm, he placed three concepts.

[00:09:34]In the noumenal realm is the idea of God, the idea of the self, and the idea of what Kant called the Ding an sich, or the thing in itself, or if you will, essences. Now, just take a deep breath here, and we'll try to get an understanding of what that's about. When he talks about things in themselves, or essences, he's talking about the metaphysical level of reality that is beyond the ability of our senses to perceive.

[00:10:17]You know, Plato, Aristotle, and other philosophers were fond of talking about the essence of a thing.

[00:10:26]And yet, we never perceive essences. We only see outward appearances.

[00:10:34]We never perceive treeness.

[00:10:37]We never perceive humanness. We only perceive particular human beings. And I don't know the soul of a person, or even if he has a soul, from observation, by analysis. I can't go to the doctor and get an examination and say, "Doctor, what kind of shape is my soul in?

[00:10:59]What are its vital signs?" Because the soul cannot be perceived by the senses.

[00:11:07]And so, all of these metaphysical realities that philosophers postulated beyond the realm of physics, that's what metaphysics is. That's which is above and beyond the physical realm.

[00:11:22]Those things cannot be known directly through sense perception.

[00:11:28]We never see them, taste them, touch them, or smell them, or so on.

[00:11:33]Those things Kant assign to the noumenal world, the self or the soul or the mind.

[00:11:42]You know, how do we know that there is such a thing as the self?

[00:11:46]And you think, "Well, that's simple. I mean, we all are aware of ourselves, that we have a certain self-consciousness."

[00:11:55]But Kant would begin to analyze that carefully from a philosophical perspective and say, "But again, how can you measure the self of the person?" And so on. So, he would put the self in the noumenal world along with God. God, the self, and essences.

[00:12:15]Now, he doesn't say that there is no such thing as God, and there is no such thing as the self, or there's no such thing as essences.

[00:12:25]For Kant, the question is epistemological.

[00:12:30]That is, the question is, can we know anything about these realities?

[00:12:39]Or if in fact they exist at all through scientific inquiry, through rational inquiry.

[00:12:49]And his answer was no.

[00:12:52]That all of our knowledge is restricted to this realm, the realm of phenomena.

[00:13:00]The phenomenal world does not mean the terrific world. Sometimes we say that somebody who's outstanding in sports, we say he's phenomenal, you know, he's fantastic, he's terrific. Now, but what this word means is phenomenal means that which can be perceived by the five senses. The It is the world of appearances.

[00:13:24]It is the world that can be studied and analyzed and examined scientifically.

[00:13:32]That is the phenomenal world.

[00:13:34]Now, what Kant was saying is that through the use of reason or of scientific investigation we cannot get from here to here.

[00:13:49]That there is an unbridgeable chasm between the world that we see and the unseen world of essences.

[00:14:01]So, we can have no real knowledge of what's up here.

[00:14:07]And one of the principal reasons he said that was because he said even though the law of causality works in the sphere in which we live, in the phenomenal world we can't know for sure that it can be applied to the metaphysical realm.

[00:14:25]So, that we cannot use the reasoning based upon cause and effect to get from the cosmos to God, to get from this world to the supernatural world.

[00:14:41]And so, he, as I said, was skeptical about the ability to know anything about God. Now, at the same time he said in his critique of practical reason that for practical purposes we must live as if there is a God.

[00:15:03]We must believe that there's a God in order for civilization to be possible because the God hypothesis, as we will see a little bit later, is necessary for meaningful ethics. And if you don't have a meaningful ethic, you can't have an enduring civilization.

[00:15:26]Without morality or law based upon objective virtue, sooner or later societies will degenerate into the law of the jungle and into anarchy where might makes right. Dostoevsky said it this way, "If there is no God, all things are permissible as law becomes reduced to preferences.

[00:15:56]And there is no such thing as what ought to be done.

[00:16:01]Only what is done. But in any case, with this skepticism, the Christian church reached a crisis.

[00:16:10]And many theologians and apologists after this critique was leveled against the traditional arguments, turned away from the classical synthesis and away from natural theology to what we call in theology fideism of one sort or another.

[00:16:36]Fideism is based upon the word for faith in Latin.

[00:16:43]And fideism simply means that we take the idea of God on faith through some kind of leap of faith. And the notion of God cannot be known rationally, and we certainly cannot prove the existence of God.

[00:17:04]You have to take it by faith or as some kind of first principle upon which you build everything else.

[00:17:12]You can maybe assume the existence of God, presuppose the existence of God, or grant the existence of God by faith, but what you cannot do is prove the existence of God by rational categories.

[00:17:28]And as I say, many philosophers and theologians capitulated to Kant at this point.

[00:17:36]Uh others, however, refused to play dead at the feet of Immanuel Kant and have sought ever since the 18th century to reconstruct natural theology in such a way as to answer the objections that Kant leveled against traditional theism.

[00:17:57]And I've been very much concerned about this undertaking in my own teaching career for this simple reason.

[00:18:05]I want to be faithful to scripture.

[00:18:09]And I find a simple conflict between what Kant taught and what is taught in the New Testament.

[00:18:19]We've already looked at the first chapter of Romans, wherein the Apostle Paul declares that the invisible things of God, even his eternal power and deity, are known through the things that are made.

[00:18:41]And so what Paul is saying is you can get here from here.

[00:18:48]He says that there is a general revelation by which God not only can be known, but is known in and through the created order.

[00:19:01]And that that knowledge is so manifest and so clear as to leave the world without an excuse. If there really is a barrier between this world and the world of God.

[00:19:17]If Kant is right, then ladies and gentlemen, the unbeliever has an excuse for not embracing the truth of God.

[00:19:30]He has the excuse of ignorance where he says, I couldn't get there from here.

[00:19:39]So, what we have here is an irreconcilable difference between the teaching of the Apostle Paul and the teaching of Immanuel Kant.

[00:19:52]And so, I look at that as a Christian and I say, well, if Paul is right, then manifestly Immanuel Kant has to be wrong.

[00:20:06]And if Kant is correct, then Paul is wrong.

[00:20:13]Again, because Kant says you can't have no knowledge of God through the knowledge of this world.

[00:20:21]Where the New Testament says, we do have a knowledge of God through a knowledge of this world. That is that God can be known cosmologically.

[00:20:35]Now, Kant went on in his critique to say that all of these traditional arguments of God are based upon the ontological argument, which is the argument from being. And the classic formulation of that was from St. Anselm who said that God is that being apart from which no greater than can be conceived. Or we turn that around and say God is the greatest conceivable being.

[00:21:07]And he says that the greatest conceivable being must be conceived of as really existing.

[00:21:16]Because if you're thinking of the greatest conceivable being as being merely a construct of the mind, just an idea with no correspondence in reality, you're not thinking of God.

[00:21:29]Because what Anselm was getting at is that God and God alone is that which no greater than can be conceived, who can only properly be conceived as being and as existing. That is to say, he's thinking of a being who cannot not be.

[00:21:53]Now, Kant challenged that and we're going to re-examine that in much greater care here fairly soon.

[00:22:01]But what Kant was saying is that from the perspective of a concept, there's no difference between a hypothetical being and a real being.

[00:22:14]Because, he said, existence is not an attribute.

[00:22:22]Existence is not an attribute. That is, there's no difference in reality between the idea of a perfect dollar and the reality of a perfect dollar.

[00:22:38]Because the concept of the dollar is the concept of the dollar. This is the same argument that was leveled against Anselm by Gaunilo, who spoke about islands. He said there's a basically just because I have an idea of the most perfect island conceivable doesn't make it true.

[00:22:57]And Anselm said, "You missed the point.

[00:23:00]I'm not talking about islands or dollars or anything else. I'm only talking in one case of that being which no greater than can be conceived and that must be conceived of being because it is greater to exist than not to exist. It's greater to be in reality than to simply be in the imagination.

[00:23:21]And so the debate continues even to our own day. But I just leave you with this now that Kant in his critique of the traditional arguments for God said that they all boil down in the final analysis to some form of the ontological argument because what what you're saying here is that if we're going to be rational, reason demands that God exists.

[00:23:50]But just because reason demands that God exist does not mean that God exists.

[00:23:58]All it means is that reason demands it, but maybe reality in the final analysis is not rational. That's why many people went from Kant's critique into a philosophy of irrationalism [music] such as existential philosophy and to relativism [music] which pervades our culture today.

[00:24:27]>> Yeah, I think it's amazing how familiar those ideas sound to us because we are living in a society that is ruled by relativism.

[00:24:35]Immanuel Kant actually said we cannot know God, let alone prove his existence.

[00:24:41]If we're going to be effective when sharing our faith, we need to be able to counter those kinds of arguments. And that's why we're featuring this series until Friday and we'll send it to you on a special edition DVD when you give a donation at renewingyourmind.org or when you call us. Our number is 800-435-4343.

[00:25:02]We'll add all of the messages to your learning library in the free Ligonier app, plus we'll give you the entire series Apologetics of the Early Church by Dr. Sproul.

[00:25:12]So, don't miss this opportunity to gain access to two series on apologetics.

[00:25:17]So, can we prove the existence of God?

[00:25:20]Today, you heard how Immanuel Kant said no, but tomorrow, R.C. Sproul will make the case that the answer is yes. Here's a preview.

[00:25:29]>> We know that what the pagan does, according to Romans 1, is that the first lie that he embraces is the denial of the eternal power and deity of God. And then his mind becomes darkened, and the more brilliant he is, the further away he moves from that first awareness of God that he gets in nature.

[00:25:51]>> Be sure to join us Thursday here on Renewing Your Mind.

[00:25:59]>> [music] [music]