A 17th century philosopher is famous for questioning everything. Did you catch that?
I hope you did. It's a real head scratcher when you think about it. Those are the thoughts, though, of Rene Descartes. He was a French philosopher and mathematician who set out to question every assumption and to build a new philosophical system. After his works were released, they caused quite a storm, and they still trouble us. Today I'm redoing your mind.
Dr. R.C. Sproul continues his series on classical apologetics by addressing the thoughts of the doubter and revealing the unshakable foundation of truth. In our last session, I outlined the four generic possibilities to explain reality as we encountered, borrowing a bit from the ancient approach of St. Augustine to this question. I'm going to repeat those four principles and look at each one in greater detail. I said if something exists, this piece of chalk or whatever it is, that we can have four possible explanations for it. The first is that it is an illusion. The second one is that it is self-created. The third is that it is self-existent. And the fourth is that it is created by something ultimately that is self-existent. And those were the four possibilities. Now, it may seem to many people to be a Herculean waste of time to really spend any time at all eliminating the first alternative, that everything that we think exists is but an illusion.
But there have been serious philosophers in history who have argued precisely that point, that the world and everything in it is simply somebody else's dream or is basically illusory and doesn't exist at all. So, in order to deal with this first principle, I'm going to call as my primary witness, Rene Descartes, the father of modern rationalism, the seventeenth century thinker who was also a mathematician, who was very much concerned in his day about a new form of skepticism that had arrived on the scene of Western Europe following the sixteenth century Protestant Reformation. Because in the wake of the Protestant Reformation, there was a crisis in authority. Previous to the Reformation, Christians, for example, in the monolithic church scene of Rome, if they had disputes could appeal to the church to render a verdict.
And when the church gave the verdict, that settled the controversy because the authority of the church was deemed to be at least sacrosanct and at best infallible. And with the challenge to the authority of the church that came with the Protestant Reformation, then the whole question of how can we know anything for sure became a serious problem for people. And not only did you see the breakdown of church authority, but you also saw the breakdown and collapse of scientific authority because in addition to the Reformation that occurred in the sixteenth century, also in the sixteenth century, the Copernican revolution in astronomy took place, which created the enormous crisis of the tradition of scientific authority that had followed in the wake of the ancient Ptolemaic system of the universe. And Copernicus upset that apple cart and raised all kinds of questions about the trustworthiness of science. This controversy over the Copernican revolution carried over into the seventeenth century where the Galileo episode became prominent in the life of the church, where Galileo, with the use of his telescope, was confirming the mathematical theories of the sixteenth century astronomers by pointing his telescope into the heavens and demonstrating the verification of these theories of the sixteenth century.
So not only in theology and philosophy, but also in science, there was a crisis of authority. And what Descartes was trying to do in his philosophical inquiry was to reestablish some foundation for certainty with respect to truth. And he was looking for what he called clear and distinct ideas, ideas that were indubitable, ideas that could not be rejected without rejecting reason at the same time, which ideas could then form a foundation for the reconstruction of knowledge, whether in the scientific sphere or in the theological philosophical arena. And so the process that Descartes followed in order to achieve certainty was to follow a plan of uncertainty or of skepticism. What he did was he embarked upon a rigorous pursuit of skepticism in which he sought to bring doubt upon everything he could conceivably doubt. In other words, he wanted to give the second glance to every assumed truth that people held.
And he asked questions, the epistemological question, do we really know that this is true? Sometimes I like to go back to first principles myself, and in fact, my whole bent in philosophical inquiry is to keep coming back to foundational principles to the fundamental truths. And I'll often make a list, and I'll say to myself, what are ten things that I know for sure? And I'll write them down, and then I'll subject those ten things to the most rigorous criticism I can to make sure that I'm not just believing them because somebody I liked taught them to me or because of my love lines, my traditions, the subculture in which I come from.
I want to know, how do I know that these things that I think are true really are true? And that principle is one of the most important principles for breakthroughs in any kind of knowledge. One of the great principles for new discoveries is the principle of challenging assumptions because that's how philosophers breakthrough, musicians breakthrough, that's how scientists breakthrough where they challenge assumptions that previous generations have been made and accepted uncritically and passed on from generation to generation, that's how the Ptolemaic system survived for over a thousand years, is by people accepting theories without the theories ever having been proved. And so we need to do that ourselves, subject our own thinking to a rigorous cross-examination because you've all seen what happens in trials where you hear somebody give their case, and you hear one side of it, and it makes sense, and you're sitting there nodding, yes, yes, yes, until the cross-examination comes and people begin to raise questions about the testimony that you've heard, and by the time you're done listening to both sides, you're not sure who's telling the truth. And so there's something valuable in that that doesn't mean you have to surrender to skepticism.
But this is what Descartes was doing. He said, I'm going to doubt everything I can conceivably doubt. I'm going to doubt what I see with my eyes and what I hear with my ears because I understand that my senses can be deceived.
And we've talked about that going back to Augustine's bent oar, you know, that you look in the water and the oar looks like it's bent, and this is what Descartes did. And he said, not only that, maybe this world is controlled by the great deceiver, a great satanic, demonic being who is a liar who constantly gives me a false view of reality, and that maybe he is the master of illusion. And so he keeps bringing these illusions in front of me to deceive me. How can I know that reality is as I perceive it to be? Remember, back to the basic foundational principles we started with, one of which was the basic reliability of sense perception. Because if we cannot trust our senses in the basic rudimentary forms, then we have no way of getting outside the interior of our minds and making contact with an external world.
And this is what is known as the subject-object problem. How do I know that the objective world out there is as I perceive it from within my own subjective perspective? And as I say, Descartes was acutely conscious of that, so he came up with some of the most preposterous possibilities and he said, now maybe it doesn't make a lot of sense to think of a great deceiver producing this vast illusion out there, but it's possible. And so if it's possible, then I can't know for sure that reality is as I perceive it to be.
So again, what can I know for sure? Well, after he went through this elaborate doubting process, he came to his famous motto or slogan for which he is so well known, the Cogito Ergo Sum, I think therefore I am. He said, no matter how skeptical I become, the one thing that I cannot doubt whenever I'm doubting what it is that I'm doubting is that I'm doubting. Because if I doubt that I'm doubting, it's necessary for me to doubt that I'm doubting so that if I doubt that I'm doubting, I have to doubt to doubt that I'm doubting. So there's no way I can escape the reality of doubt.
You say, well, I doubt it. Well, if you say I doubt it, you have proven the very point in dispute. He says the one thing about which there's no doubt is that I'm doubting.
Because if you doubt that, you prove my premise. And so he came to the conclusion that there's no doubt that I'm doubting. And then he raised this question, what is required for there to be doubt? Well, he said for there to be doubt, doubt requires cognition. Doubt requires thought, conscious thought, because doubt is an action of thinking. Without thinking, there can be no doubting. So if I'm doubting, I know what?
That I'm thinking. Now, at least I think that I'm thinking. And you say you don't think that I'm thinking? Well, in order for you to say you don't think that I'm thinking, you must be thinking. So I can't escape the reality that I am thinking, because to doubt is to think. And then he goes to the next premise that just as doubt requires a doubter, just as thought requires a thinker, so if I'm doubting, I must conclude rationally that I'm thinking. And if I'm thinking, I must be. I must exist, because that which does not exist cannot think. That which cannot think cannot doubt. And since there's no doubt that I'm doubting, it would mean also that I'm thinking. And if I'm thinking, I am also existing. And so I come to the conclusion. He says, Cogito, I'm thinking. Ergo, therefore, sung I am. Now, people who are not students of philosophy look at that elaborate process that Descartes goes through and say this is why philosophy is so foolish, that somebody would spend all this time and all this effort to learn what everybody already knows, who's alive and awake and conscious, that they are, in fact, existing, that nobody really is denying their own existence.
They're not really believing that they are simply a star appearing in somebody else's dream. But again, remember what Descartes was about. He was a mathematician, and he was looking for certainty at the philosophical realm that would equal in force and power and rational compulsion the certainty that can be arrived at in mathematics.
And so he goes through this process, and he wants to get a primary principle. He says, so that I can then crawl into my Dutch oven and then use the art of deduction where I'm not dependent upon my senses to come to an understanding of truth. And so I begin with a knowledge of my own self-consciousness.
I said two lectures ago when we talked about presuppositional apologetics that for classical apologetics the starting point is not God consciousness because we say only God can start there, but the epistemological starting point of Christian apologetics has to be self-consciousness where you start in your own mind because that's the only mind you have at your disposal and that all thought begins with an awareness of a conscious awareness of one's thinking or one's existence. So that what Descartes is getting at here is whatever else may be in doubt, the fact that I am a self-conscious existing person is not in doubt and that I do not have to look at my feet to know that I exist. I am not dependent on any external perception. I am now learning this just simply from the interior processes of thought in the mind.
I'm not dependent on external data. So he stays within the realm of rational deduction for his conclusion. Now, the reason this is important is that Descartes is disposing with the first option that reality is an illusion. There may indeed be illusions in reality, but if we say that all reality is illusion, that would mean that nothing exists, including myself, and I can never even doubt the existence of myself without proving the reality of myself. That's the point he's trying to get at, that that first of the four alternatives as a sufficient reason to account for the universe has to be discarded because his argument proves that something exists, and that something that exists, if nothing else, is his own consciousness. In other words, to put it another way, is that if I think that this piece of chalk is an illusion, and it may be, I didn't say that this piece of chalk proves the existence of God. What I'm saying is that if this piece of chalk actually exists, then it would prove the existence of God. But this piece of chalk might be an illusion, and so I have to take a little different tack there and say if anything exists, then God must exist. That way I'm not hidebound to this particular bit of reality, the piece of chalk, because maybe this piece of chalk is an illusion.
I don't think it is, but it could be theoretically. But what I have to establish if my system is going to work is that something exists, and there I thank Descartes for solving that problem for me by proving the existence of himself. Now what are the things that he's assuming in order to arrive at his conclusion? I mean there are philosophers who don't agree with this premise, Cogito Ergo Sum, who still insist that there's no basis in reality for his coming to that conclusion.
And they point out correctly, at least this far, that there are certain assumptions that Descartes is making along the way in order to come to this conclusion. And there are two major assumptions that he's making in order to come to the conclusion that because he's doubting, he must be thinking, and because he's thinking, he must be existing. The first assumption that he is making clearly is the epistemological principle of the law of non-contradiction. He's assuming logic. He is assuming rationality, isn't he? Because he's saying, if I am doubting, if I doubt that I'm doubting, then I must be doubting. That is a logical conclusion based upon the law of non-contradiction, where the existential irrationalist may say, well, so what that it's irrational?
He can still be living in an illusion where doubters can doubt without doubting. And that's what irrational people say. But remember that classical apologetics is only trying to show that reason requires the existence of a self-existent eternal being. If somebody is an atheist and said, I don't believe in the existence of God because I don't believe in rationality, I give them the microphone and say, please tell the whole world that your alternative to theism is absurd. Save me the problem and the difficulty of having to demonstrate it.
I don't have to demonstrate it if you acknowledge it. But I mean, they have taken themselves out of any intelligent discussion as soon as they admit that their premise is one of irrationality. What Descartes is trying to say is just as mathematics is rational, just as sound science is rational, so sound philosophy must also be rational. And if you are going to be rational and if you are going to be logical, you cannot deny that to doubt you must doubt. And then the second premise that he is assuming is the second law that we talked about at the beginning of this course, which is the law of causality. When he says that doubting requires a doubter, he is saying that doubt is an effect that requires an antecedent cause. So some of the critics of Descartes would say, oh, well this doesn't prove that he exists because he's assuming logic and he's assuming causality, and we don't accept those premises.
And we say, okay, that's fine. If you want to be irrational, because remember we saw that the law of causality is simply an extension of the law of non-contradiction, that the law of causality that says that every effect must have an antecedent cause is a formal truth. It's as formally true as two and two is four, because it's true by definition. So if we assume, remember I said at the beginning, you dare not negotiate the law of non-contradiction, and you dare not negotiate the law of causality, because if you do, you'll end up in absurdity. But if you use these principles that are necessary for all intelligible discourse in all science, in all philosophy, in all theology, then you cannot escape, I don't think, the conclusion that Descartes gives that we can, through a resistless logic, through formal reasoning alone, come to the conclusion of our own existence, which then satisfies that first premise about illusion, and we can eliminate that as one of the possible alternatives for sufficient reason for the existence of the world.
That's Dr. R.C. Sproul showing us how logic is a useful tool in apologetics. We're glad you've joined us for the Saturday edition of Renewing Your Mind. Each week we return to Dr. Sproul's series Defending Your Faith. We as Christians are called to give an answer for the hope that is within us. In 32 Messages, Dr. Sproul does just that.
He looks at the history of apologetics and helps us defend the historical truth claims that we find in Scripture. We'd like to send you the 11-DVD set when you contact us today with a donation of any amount. There are two ways you can reach out to us to make your request.
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It provides the study guide for each session, also the outline for the session, further reading suggestions, and sample study questions. So if you lead a Sunday school class at your church or perhaps a Bible study at your home, you'll find that bonus disc helpful. We'll send you all 12 discs when you call us today for a donation of any amount. Again, our phone number is 800-435-4343.
Our online address is RenewingYourMind.org. Hearing Dr. Sproul's message today reminds us of just how important it is to understand our faith. The floodgates have opened wide, haven't they, with the advent of social media and strange philosophies that are running rampant. It's no wonder that so many people are confused.
Our goal here at Ligetor Ministries is to provide you with sound biblical teaching to help you know what you believe and why you believe it. And that's why we're thankful for your support. You know, as we learn more about how to defend Christianity, it's easy to forget that our unbelieving friends and neighbors are firmly convinced of their beliefs. It's easy to think that we have faith, and they don't. But next week, R.C. will point out that it takes a tremendous amount of faith to believe that the world created itself. I hope you'll join us next Saturday for Renewing Your Mind. you
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