Transcript Reading: Continuing Descartes

I know we haven’t gotten very far yet into our cast of philosophers to be investigated. We’ve said a few things about Hobbes, who isn’t that important to this era, but we started with him because, chronologically, he’s in the period we’re studying. Then, we switched to began to talk about Descartes. I think it might be a good idea to review what we’ve done so far. Even though it hasn’t been much, it’s been very important. I want to start with a quick review of some of the basic concepts I introduced in the first few talks, starting with the definition of religious belief. Let’s use my blackboard here.

A religious belief is any belief in something as the self-existent origin of all else. If someone believes in more than one of these things, they might think there are two self-existent beings—neither of which is the origin of everything else, because they might divide reality up. One might be the origin of these things over here, and the other, a different kind of thing over there that we find in our created cosmos. But between the two of them, they account for the origin of everything else. So, with that qualification, I think this definition stands up. It stands up to all kinds of scrutiny, including historical scrutiny. If you look at the history of religions—and I’ve read about dozens and dozens of them—each has something at the center of its system that is the self-existent origin of all else, and that is the definition of the divine. So any belief in that is what I call a divinity belief.

Now, notice that I’m saying whatever is put in that spot is divine to the people who believe in it. This definition is independent of any specific description of the divine reality. I pointed out how this was recognized even in the ancient world. Anaximenes had come up with this before 600 BC, and Aristotle and Plato endorsed it. It was common knowledge in the ancient world. They all accepted that the divine was what did not depend on anything, did not come into being, did not pass away, and other things depended on it, while it didn’t depend on anything.

Of course, they had many different descriptions or proposals as to what that was. You remember some of them: the famous Earth, air, fire, water as the uncreated, self-existent stuff that generates everything else. The Pythagoreans said it was numbers. Plato said it was forms and matter: there has to be some stuff, and then there have to be the perfections—the realm of all the truths in math and logic and all the perfections that somehow impress themselves on matter, so that matter ends up as an organized cosmos instead of just chaos. Many different proposals exist about what is divine. Some people are surprised to hear that the Pythagoreans put numbers in that category, but they did. In fact, in my first book, I quoted a Pythagorean prayer to the number 10. Weird stuff, okay, but they were searching the cosmos for what is the divine reality that has generated everything else. That’s the way their theories of reality all begin.

Theory of reality has a proper name in Greek, and it was the Greeks who invented theory-making and philosophy. Its name is ontology. One big part of philosophy is ontology: what does the thinker say is the nature of reality? After they give us a theory of reality—usually after it, but later thinkers will turn this around—they give us a theory of knowledge. The ancient Greek philosophers did this, so did the medievals, and so did almost everybody in this period we’re studying: the modern period. The theory of knowledge also has a technical name: it’s epistemology. That’s a theory of the nature of the best knowledge we have—knowledge that’s sure and certain. In this period we’re studying, people still did that. They gave an ontology and epistemology. Descartes is going to do that, and so will the others we study after him until we come to the last thinker of this period: Immanuel Kant.

Kant’s going to turn it upside down and say, “No, people have been doing it backward all these centuries. First, you have to get a theory of knowledge. You have to examine the human mind and how it works, and get a theory of how it works, what it can know, and what it can’t. Then, see if one of the things it can know is a theory of reality.” His conclusion is that you can’t do it. So, we can have a theory of knowledge, but we can’t get a theory of reality. He calls that metaphysics and dismisses it. It’s a dismissive term as he uses it.

Given this brief review, we see that the divine is whatever a theory or a person regards as the self-existent origin of everything else, and all ontologies start with that. Both in the ancient world, the medieval period, and the modern period up to Kant, they all start with a theory of reality, then give us a theory of knowledge. They also give us other things, which we’re going to look at—for example, a theory of human nature, human society, political philosophy, a theory of the state and law—and they try to hang it all together based on the theory of reality they give. We’ll see if Kant can really succeed in turning it all upside down. He claims to have come up with a theory of knowledge that doesn’t need any assumptions about reality in order to be constructed, and I think he fools himself. So, we’ll see about that when we get to the fun and games yet to come, folks—we’re going to have a good time.

We then took the first philosopher to live in this period we’re studying, and that was Thomas Hobbes. He is unlike any of the philosophers after him or before because Hobbes answers the question of the nature of reality by saying it’s physical. All reality is purely physical or caused by the purely physical. He’s a materialist. In philosophy, being a materialist doesn’t mean you’re concerned only with the number of possessions you can acquire. It doesn’t mean you’re only concerned with how much money you have or how many homes and cars you own—that’s a different sort of ethical materialism. We’re talking about a theory of reality that says reality is essentially physical, and that’s what Hobbes held. He believed there are little, tiny particles that are purely physical, which go into all sorts of combinations and make up everything else.

If that sounds roughly like early atomic theory, it is a lot like it. Hobbes didn’t have as sophisticated an idea of the atom as we do now, but essentially, there are tiny physical things, and how they combine determines whether what they combine into is a planet, a tree, an ocean, a horse, or a human. Hobbes didn’t want to get into trouble by leaving his theory there, so he added that he believed in God. I don’t know whether he said that just to keep himself out of jail or if he really meant it, but let’s take him at his word. He thinks there’s a creator—who’s not physical, by the way—who brought the physical world into existence. So his ontology about creation, about the cosmos in which we live, is that he’s a materialist. But if he’s sincere about this, his entire position is that everything consists of God or physical objects—physical things.

He also thought that math was the way to explain the physical order of the universe. He was as impressed as anybody else with the accomplishments of Kepler, Galileo, Newton, and so on. He was very impressed with how they were applying math to the created world and coming up with explanations that seemed convincing—great improvements over anything anyone had before them. These successes in astronomy and physics particularly impressed the heck out of everybody. In fact, in this period, everyone we’re studying was an extraordinary genius, but the most towering genius of the entire period—the one person they all would have pointed to and said, “Everybody wants to do what this guy did”—was Isaac Newton, who didn’t write philosophy. He did physics and theology. In fact, he wrote way more theology than he did physics, but he was considered the exemplar par excellence of the towering genius who comes to a field that’s in complete disarray, figures out some basic laws, comes up with mathematical formulas to apply them to reality, and suddenly, all of these disparate things that seemed to have no connection are connected and explained by the same basic principles.

That is the towering achievement of the age. They all would have told you they revered Newton.

Hobbes was just as impressed with Newton as anybody else, and he thought that math was the way to go. So, in what epistemology he did write—in theory of knowledge—he affirms math as a methodology, but he’s not considered a rationalist. So, what is a rationalist, then? Well, a rationalist isn’t just somebody who thinks, “Okay, there are rational laws, the laws of logic and mathematics.” No, a rationalist thinks those laws determine the basic fabric of reality.

Let me see if I can give an illustration to show this difference. For Hobbes, all our knowledge comes through sense perception. We see, taste, touch, hear, and smell the world around us. That’s how we get our information. If we want to organize and explain that, we add mathematical formulas, and we try to do it the way Newton and Galileo did. All right. Now, compare that to someone like Descartes, and I’m going to begin the review of what little we’ve covered of him. For Descartes, math and logic—and he viewed them as pretty much the same thing—give us the fabric of reality. So, for Hobbes, we know the world around us through sense perception, and then we try to organize and explain things by using math and logic. But for Descartes, we know math and logic first, and then we try to figure out what the world is like, including perceptions.

Descartes is going to raise the issue: can we trust our perceptions? How do we know our perceptions reveal the world as it is outside of us? After all, perceptions—and this is common to all the people in this period—they all hold this: perceptions are things that occur in here. They occur in brains or in minds; they’re inside us. How do we know they show the world the way it is? In fact, how do we know that the perceptions we have are not just an internal virtual reality show, and that there is no external world at all? How can we trust them?

Hobbes assumes we can and says that’s where we get our information, and then we try to organize it with math. Descartes, on the other hand, says what we primarily know, what we know for sure, includes math and logic, which the sciences use. But from math and logic alone, we can then say whether perceptions are reliable.

And his conclusion is that they are. He thinks he can offer us a proof—a logical proof—that perception reliably conveys to us what the external world outside our minds is really like. Not only that, but logic, he says, can give us proof that God exists. Logic can give us proof that the human soul is immortal. There are all kinds of things that, just from rational principles, can be proven to be true, which then set us off on a theory of reality and knowledge. Descartes starts with these basic fundamental truths, and that’s where we are today. We’re going to begin to look at how Descartes tried to bring this off.

And, of course, I think you know that one of the first things Descartes recommended was what he called methodological doubt.

We’re still reviewing now—I covered that a bit last time. His method is going to be that we’ll approach the whole of human experience and put into the bin of “doubtful until proven” anything that isn’t undeniable. If something can be doubted, or if there’s any reason it could be wrong, simply that we’ve got no good reason to think it’s not wrong, it goes into the bin of doubtful.

Now, we’re not really doubting that there’s an external world or that other people exist. He doesn’t mean that—that’s why he calls it methodological doubt. It fits into the method of his theory of reality and knowledge. His theory of knowledge is going to start by doubting everything that can be doubted and see what’s left. And whatever’s left, that’s what we’re going to start with.

Remember, in my earlier talk, when I discussed the century before this one, I described it as a century of upheaval and turmoil. There were three great cultural forces that collided in the 16th century: the established medieval order of the traditional church and state, the Renaissance, trying to revive rationalism from the ancient world, and the Reformation, trying to restore the church and the gospel to what it regarded as its original form. So, each one called the other into question

The Renaissance rejected both the traditional church and the Reformation. The Reformation saw what was wrong in the traditional church, in their opinion, and viewed the Renaissance as just the revival of paganism. Out of that conflict, people were left in grave doubt about everything—all of the customs, traditions, and beliefs that were once thought to be true were now being called into question by someone. Descartes wanted to start fresh, sweeping away everything that could possibly be doubted, and asking, "Is there anything left? Is there any truth that nobody could reasonably doubt, that no one could deny?" When he did that, his answer was, "Yes, there is one."

And I'm writing this in Latin, not because I know Latin, but because it's famous in its Latin form: Cogito, ergo sum. This was actually taken from St. Augustine, who had written, "If I doubt, I must exist." In other words, doubting or thinking—when Descartes says, "I think, therefore I am," he means any kind of mental process. If I can think at all about anything, if I’m aware of anything, if I’m conscious of anything, I must exist. I have to exist to be conscious. Then he says the reason for believing this is that it is, in his words, "so clear and distinct" that there is no room for doubt.

I think Descartes was onto something when he proposed, "I think, therefore I am." That seems to be absolutely right, but not for the reason that it’s clear and distinct. I can think of a lot of clear and distinct ideas that do not correspond to realities—a flying carpet, for example. And as just about everybody in philosophy knows, there are great controversies in mathematics about the axioms of math. All of the proposals are clear and distinct, yet they cannot all be true. They’re in logical conflict with one another; some are contradictory, some are contrary. They can’t all be right, but they’re clear and distinct enough—that’s how we know they’re incompatible with each other. So, I don’t think Descartes’ explanation of why the Cogito is right is the correct one.

I think it’s simply this: in order for you to perform any action, whether it’s bodily or in your mind, you’d have to exist. To deny that is what I call "self-performatively incoherent." If you have to perform a certain action in order to know x, y, or z, then x, y, or z can’t include that you don’t exist. You have to exist to perform the action. That’s it. So, I think Descartes was correct, but what he does then is take the second part of his statement—that the reason the Cogito is right is because it’s "so clear and distinct"—and uses that to justify other clear and distinct ideas. These other clear and distinct ideas include logic, mathematics, and some axioms about knowledge. One of them, for example, is the principle of sufficient reason, which we’ll talk about shortly.

There are a number of things that Descartes tries to derive from this principle of clear and distinct ideas that can’t be wrong. Now, I have a suspicion about what’s going on there, and I’ll share it with you. The old-time name for seeing the truth of a statement without any proof is to say it’s "self-evident." That’s the traditional name. If I’m confronted with a proposal and I read that statement, and it looks to me—on the face of it, prima facie—as true, and it’s not derived from any other truth, then it meets the conditions for being called self-evident.

In the ancient world, Aristotle explained this very clearly and asserted that there were many things that were self-evident, and we couldn’t know them any other way. So, self-evidence is a necessary and reliable component of knowledge, but it has restrictions. Aristotle added that a truth must also be self-evident to all other experts in the field where this truth arises, and that the truth has to be a law. If it is self-evident to everyone and is a law, then it is also infallible—it cannot possibly be false.

My point to you is that we all have the experience of seeing things as self-evidently true, and that’s not just the case with statements. Normal sense perception is taken to be a self-evident display of the world around us. Everyone regards it as such, from morning to night, every day. Everybody, everywhere, regards their perception as showing them the world as it is. It doesn’t show everything about the world—it doesn’t show the subatomic level—but it shows us the surface level of the world as it is. Everybody thinks that, until they’re given some clever philosophical argument that tries to convince them otherwise.

Now, Descartes didn’t give us yet a clever philosophical argument that perception can’t be trusted, but he did throw perception into the bin of things that are doubtful until proven. Later on, he did give some arguments. He pointed to hallucinations. He pointed to realistic dreams. He said, “At times I’ve had a dream that I didn’t know was a dream until I woke up, but while I was dreaming, that wasn’t reality. I was perceiving an illusion.” He gives those reasons why perception can’t just be declared reliable, because there are unreliable perceptions. So, he sets off on the project of proving that, except for hallucinations and realistic dreams, perception is reliable.

Today, we would add holograms to the list, I guess—they can also deceive us—but Descartes didn’t know about those. He wanted to determine what it is that goes into the class of sure and certain, reliable beliefs that are so clear and distinct that there is no room for doubt. What else can go in there that is enough like Cogito, ergo sum that it can be counted, too? He’s going to say the principles of mathematics, logic, and some other axioms can be included. Then he’s allowed to use them—that’s his procedure. All of them come up unscathed when you try to doubt them; there’s no reasonable way to doubt them at all.

The fundamental axiom of logic is the principle of non-contradiction. Consider the principle of non-contradiction and see if there’s a way to doubt it. It says no statement can be both true and false at the same time in the same sense. So, if I borrowed $20 from you and I haven’t paid you back, I can’t say, “Well, it’s just as true that I did pay you back.” No. I either paid you back or I didn’t, but it can’t be both. And it can’t be neither. Either I paid the debt or I didn’t. You would never let me get away with saying, “Well, it’s just as true that I did as that I didn’t, so I’m not going to pay you.” You’d say, “Yes, you are, because you owe me.”

That’s one example of something that can’t be doubted—the law of non-contradiction. There are people who try to doubt it, but they employ it while denying it. The same thing is true about some basic mathematical truths and other axioms, and we’re going to talk about them as well.

This is the point at which, if I were in your classroom, I’d now say, “What questions do you have?” I can’t do that here, so I have to assume the review has helped and set some things in greater clarity. Now, we’re going to go ahead with Descartes, who proposes to offer us a proof that normal sense perception is reliable and shows us the world the way it is.

If you took on that task, how would you go about it? Well, here’s how Descartes went about it.

Here's Descartes' argument, presented step by step:

Premise One: The Principle of Sufficient Reason
This principle says that for everything, there must be a cause or an explanation. We naturally assume that everything that happens has a reason behind it, but the principle goes further than that. It doesn't just say that everything in fact has a cause or explanation—it says that everything must have one. So, if someone proposes an idea in a theory that cannot possibly have a cause or explanation, anyone subscribing to the Principle of Sufficient Reason would have to deny that idea, rejecting it because it lacks a cause or explanation.

Even Aristotle, who was very cautious about what counts as self-evident, didn’t balk at this one. He thought that everyone knowledgeable in this field would concede that it's true, that it's a rule of reality, and therefore, it's infallible. Descartes didn’t want to run afoul of Aristotle's three restrictions on self-evidence. In fact, he endorsed them but added his own twist. For Descartes, something isn’t just self-evident to experts—it’s self-evident to anyone who is at least somewhat rational. If you're not crazy or irrational, you should be able to recognize these truths. He agreed that these principles must be laws, and because they are laws, they are infallible.

Premise Two: Causes Are Always Equal to or Greater Than Their Effects
Why should we believe that causes are always equal to or greater than their effects? Descartes would say that it's grounded in the Principle of Sufficient Reason. Imagine an apparatus that uses a stream of water to turn a paddlewheel, which in turn pumps water. The amount of water pumped can't be greater than the amount flowing into the apparatus—if more water were pumped than the cause could account for, then some of it would have no explanation. The same logic applies to any cause: if the effect were greater than the cause, it would violate the Principle of Sufficient Reason because there would be something that lacks a cause.

Premise Three: There Exists in My Mind an Idea of Infinity
Descartes argues that we all have an idea of infinity in our minds. He doesn’t mean quantitative infinity, like numbers that go on forever. Instead, he’s talking about qualitative infinity—something that has all and only perfections. This idea goes back to Plato, who believed that for every imperfect thing we see in this world, there’s a perfect version in another realm. Descartes doesn’t necessarily subscribe to Plato’s idea of another world full of perfections, but he does believe in the concept of perfection. For Descartes, the idea of infinity refers to a being that has every possible perfection—omniscience, omnipotence, perfect goodness, etc. He acknowledges that theologians before him used this concept of infinite perfection to describe God, and he’s using it in the same way.

Conclusion: Therefore, There Exists an Infinite Cause of My Idea of Infinity
Descartes elaborates on this: the idea of infinity in my mind can’t come from my perceptions of the world because we don’t see perfections in the world. Even when we draw a line or a circle in geometry, it’s never perfect—we only say it represents a perfect line or circle. So, where does the idea of perfection come from? If I had come up with it myself, my mind would have to be infinite, and I know for a fact that my mind is not infinite. Therefore, my idea of infinity must have been caused by something that is infinite—an infinite being.

This leads Descartes to his conclusion that there exists a being with all and only perfections, which is traditionally understood to be God.

Part Two: God Cannot Deceive Us
Descartes then moves on to his next premise: God cannot deceive us. Why not? Because deception is an imperfection, and if God has all and only perfections, then God must have infinite honesty.

Now, Descartes proceeds with the next premise: If normal sense perception did not show us the world as it truly is, then God would be a great deceiver. But since God cannot deceive us, it follows that our normal sense perceptions do, in fact, show us the world as it is.

Descartes argues that our perceptions are reliable because God, who is infinitely honest, wouldn’t deceive us by giving us perceptions that misrepresent reality. If our senses were unreliable, then God would be tricking us, and that’s impossible because deception is contrary to God's perfect nature.

So, Descartes concludes that normal sense perception does convey to us the world as it truly is.

When I initially said that Descartes was going to prove that sense perceptions are reliable, you probably didn’t expect him to use this kind of argument, but that’s exactly how he approached it. First, he proves the existence of God based on principles that are self-evident or, in his words, so clear and distinct that they can’t be false. These principles include the Principle of Sufficient Reason and the Principle of Causality. By applying these to his idea of God, he concludes that the only thing that could have caused this idea of infinity is an infinite being—God. Since God is infinitely honest, He wouldn’t deceive us into thinking that our perceptions are reliable if they weren’t. Therefore, normal sense perception must show us the world as it really is.

In summary:

1. For everything, there must be a cause or explanation (Principle of Sufficient Reason).
2. Causes are always equal to or greater than their effects (Principle of Causality).
3. There exists in my mind an idea of infinity, which means an idea of something with all and only perfections.
4. Therefore, there exists an infinite cause of my idea of infinity, which is God.
5. God cannot deceive us because deception is contrary to infinite perfection.
6. If normal sense perception didn’t show us the world as it is, God would be a great deceiver.
7. Since God cannot deceive us, normal sense perception conveys to us the world as it truly is.

This is Descartes’ argument, step by step, and it forms the foundation of his proof that we can trust our perceptions of the external world.

Descartes' Method and Ideas:

Now that Descartes has established, through his argument, that we can trust our perceptions, that God is real, and that God wouldn’t deceive us, he feels confident that we can scientifically investigate the world around us. However, Descartes himself was more interested in the abstract, focusing on the logic and mathematics that he believed were grounded in self-evident truths that couldn’t be doubted. As you may know, Descartes invented analytic geometry, and that was a key achievement that made him famous across Europe.

But what led to Descartes' demise wasn’t his work in mathematics or philosophy—it was his personal habits. Descartes had a peculiar routine: he liked to stay in bed until noon every day, where he would write, read, and reflect. His nightlife was also quite active, as he often attended social events and parties. But when Queen Christina of Sweden invited him to become her tutor, things changed. He initially declined, but eventually accepted due to financial difficulties, even though he wasn’t keen on the idea.

Sweden's long winters and bitter cold were already challenging for Descartes, but what made matters worse was that the Queen expected lessons to begin at 5 a.m. every day—a far cry from his late-morning routine. The combination of the early hours, the cold climate, and lack of sleep took its toll. Descartes soon contracted pneumonia and, sadly, passed away at the age of 55. His death came just as his work was gaining momentum, and he never lived to see the controversies or the criticisms that would later arise about his theories.

With that, let's dig deeper into Descartes’ famous argument.

Evaluating Descartes’ Proof:

Let's take his argument, one premise at a time.

Premise 1: The Principle of Sufficient Reason
The Principle of Sufficient Reason (PSR) states that everything must have a cause or explanation. At first glance, this seems obvious—everything in our experience appears to have a cause. But Descartes didn’t just say that everything in fact has a cause; he said it must have one. This is a key difference: even if something seems inexplicable, the PSR demands that there must be an underlying reason for it.

However, the principle raises questions. If Descartes' belief in the PSR is rooted in his belief in God as the Creator of everything, then his argument becomes circular. He’s using the PSR to prove the existence of God, but if his reason for believing the PSR is based on God’s existence, then he’s assuming what he’s trying to prove. That’s called "begging the question"—a logical fallacy where the conclusion is assumed in the premises.

Premise 2: Causes are Always Equal to or Greater Than Their Effects
This premise makes intuitive sense. Descartes suggests that a cause must be at least as powerful as its effect. If a machine is powered by a certain amount of energy, it can’t produce more energy than what’s put into it. This seems reasonable, but Descartes presents it as an axiom, a self-evident truth, rather than something demonstrated by experience. While the idea may seem valid, Descartes doesn’t explain why it must necessarily be true.

Premise 3: There Exists in My Mind an Idea of Infinity
This premise is crucial to Descartes’ argument. He claims that he has an idea of infinity—an idea of something with all and only perfections. But Descartes doesn’t mean quantitative infinity (like the endless sequence of numbers); he means qualitative infinity—a being that has every possible perfection, such as omnipotence, omniscience, and perfect goodness. He identifies this being as God.

Conclusion: Therefore, There Exists an Infinite Cause of My Idea of Infinity
Descartes argues that since he has an idea of infinity, there must be an infinite being that caused it. The Principle of Sufficient Reason says that every effect must have a cause, and the cause must be equal to or greater than the effect. Since the idea of infinity cannot come from finite things like the world around us or from our own minds (which are imperfect and limited), Descartes concludes that only an infinite being could have caused this idea.

Evaluating Descartes' Use of the Idea of Infinity:

The problem with this proof lies in how Descartes uses the term "idea of infinity." At first, he refers to the idea of infinity as something in his mind, which is fine. But when he concludes that the idea must have an infinite cause, he switches the meaning. The idea in his mind is just a concept—it’s not actually infinite. It’s the idea of something infinite, not an infinite thing itself. His argument assumes that the idea of infinity in his mind requires an infinite cause, but that’s a leap.

This fallacy, called equivocation, occurs when the same word or phrase is used in different ways within an argument. Descartes starts by talking about an idea in his mind, but then treats the idea as if it were something that itself required an infinite cause, which is not the same thing. His idea of infinity is finite, just like all other ideas in his mind.

Part Two of Descartes' Proof: God Cannot Deceive Us
In the second part of his argument, Descartes claims that God cannot deceive us because deception would be an imperfection, and God is a being with all and only perfections. Therefore, if God made our perceptions unreliable, He would be a great deceiver, which is impossible. So, Descartes concludes that normal sense perceptions must show us the world as it is, because God wouldn’t deceive us.

Conclusion:

This argument is creative, but I don’t find it convincing. The central issue is that Descartes equivocates on the term "idea of infinity," treating it as something that requires an infinite cause, even though the idea itself is not infinite. Moreover, Descartes' reliance on the Principle of Sufficient Reason and the Principle of Causality is based on the assumption that these principles are self-evident truths, when they might be more open to doubt than he admits.

Descartes’ proof may not be airtight, but his attempt to ground philosophy in clear and distinct ideas was groundbreaking. His influence on modern philosophy is immense, and his method of methodological doubt set the stage for centuries of philosophical inquiry.

Next time, we’ll continue our exploration of Descartes’ system and examine how he built an entire worldview on these foundational ideas.