Doubt Everything

Rene Descartes

A Brief Introduction to Descartes

Demolishing My Opinions

 

 

Some years ago I was struck by how many false things I had believed, and by how doubtful was the structure of beliefs that I had based on them. I realized that if I wanted to establish anything in the sciences that was stable and likely to last, I needed—just once in my life—to demolish everything completely and start again from the foundations. It looked like an enormous task, and I decided to wait until I was old enough to be sure that there was nothing to be gained from putting it off any longer. I have now delayed it for so long that I have no excuse for going on planning to do it rather than getting to work. So today I have set all my worries aside and arranged for myself a clear stretch of free time. I am here quite alone, and at last I will devote myself, sincerely and without holding back, to demolishing my opinions.

 

I can do this without showing that all my beliefs are false, which is probably more than I could ever manage. My reason tells me that as well as withholding assent from propositions that are obviously false, I should also withhold it from ones that are not completely certain and indubitable. So all I need, for the purpose of rejecting all my opinions, is to find in each of them at least some reason for doubt. I can do this without going through them one by one, which would take forever: once the foundations of a building have been undermined, the rest collapses of its own accord; so I will go straight for the basic principles on which all my former beliefs rested.

 

Whatever I have accepted until now as most true has come to me through my senses. But occasionally I have found that they have deceived me, and it is unwise to trust completely those who have deceived us even once.

Doubt and Rational Foundations

It's important to remember that Descartes was writing The Meditations during what is known as the "early-modern" era of philosophical history. Heavily influenced by the enlightenment, he wanted to establish the rational foundations for his beliefs himself, rather than deferring to authorities like scripture, tradition, or the clergy (something modern philosophers often accused medieval philosophers of relying too heavily on).

Descartes Attempts to Doubt His Senses

...Whatever I have accepted until now as most true has come to me through my senses. But occasionally I have found that they have deceived me, and it is unwise to trust completely those who have deceived us even once.

Yet although the senses sometimes deceive us about objects that are very small or distant, that doesn’t apply to my belief that I am here, sitting by the fire, wearing a winter dressing-gown, holding this piece of paper in my hands, and so on. It seems to be quite impossible to doubt beliefs like these, which come from the senses. Another example: how can I doubt that these hands or this whole body are mine? To doubt such things I would have to liken myself to brain-damaged madmen who are convinced they are kings when really they are paupers, or say they are dressed in purple when they are naked, or that they are pumpkins, or made of glass. Such people are insane, and I would be thought equally mad if I modeled myself on them.

Descartes initially finds his project more difficult than he'd imagined. He acknowledges that sometimes his senses mislead him, but wonders whether only the insane could doubt all beliefs formed through the senses.

But Descartes acknowledges that it's perfectly normal to have very vivid dreams. Since, he claims, he can't reliably know whether he is sleeping or awake, he can doubt the general reliability of his senses by supposing that he may be asleep.

What a brilliant piece of reasoning! As if I were not a man who sleeps at night and often has all the same experiences while asleep as madmen do when awake—indeed sometimes even more improbable ones. Often in my dreams I am convinced of just such familiar events— that I am sitting by the fire in my dressing-gown—when in fact I am lying undressed in bed!

Yet right now my eyes are certainly wide open when I look at this piece of paper; I shake my head and it isn’t asleep; when I rub one hand against the other, I do it deliberately and know what I am doing. This wouldn’t all happen with such clarity to someone asleep.

Once again, Descartes questions the possibility of his method of doubt: can we really suppose we're asleep when it seems so obvious to us that we're awake?

In the end, though, Descartes succeeds in doubting his senses by recalling dreams he's had where he's been wrongly convinced that he was awake. Because such errors are possible, Descartes thinks, he has adequate grounds to doubt beliefs formed through his senses.

Indeed! As if I didn’t remember other occasions when I have been tricked by exactly similar thoughts while asleep! As I think about this more carefully, I realize that there is never any reliable way of distinguishing being awake from being asleep. This discovery makes me feel dizzy, which itself reinforces the notion that I may be asleep!

 

The Dreaming Argument

The Argument Illustrated

Further Discussion

Here's one way we might represent the logic of Descartes dreaming argument:

1. If I know something, it is because my senses have not deceived me.

 

2. When I sleep, my senses deceive me.

 

3. I cannot know whether I am awake or asleep.

 

4.Therefore, I cannot know anything.

Do you think the argument is successful? If not, which of the three premises would you question, and how would you go about arguing against that premise?

Consider the following illustration of Descartes's argument from the movie Inception (2010):

Dreaming has long been a topic of philosophical speculation. To read more about the philosophy of dreaming, click here.

The Dreaming Argument

Objection: even in dreams some things are certain

 Here, he considers the possibility that mathematics (or some similar domain of knowledge) could be left untouched by his dreaming argument.

Suppose then that I am dreaming—it isn’t true that I, with my eyes open, am moving my head and stretching out my hands. Suppose, indeed that I don’t even have hands or anybody at all. Still, it has to be admitted that the visions that come in sleep are like paintings: they must have been made as copies of real things; so at least these general kinds of things— eyes, head, hands and the body as a whole—must be real and not imaginary.

 

For even when painters try to depict sirens and satyrs with the most extraordinary bodies, they simply jumble up the limbs of different kinds of real animals, rather than inventing natures that are entirely new. If they do succeed in thinking up something completely fictitious and unreal—not remotely like anything ever seen before—at least the colors used in the picture must be real. Similarly, although these general kinds of things— eyes, head, hands and so on—could be imaginary, there is no denying that certain even simpler and more universal kinds of things are real. These are the elements out of which we make all our mental images of things—the true and also the false ones. These simpler and more universal kinds include body, and extension; the shape of extended things; their quantity, size and number; the places things can be in, the time through which they can last, and so on.

 

So it seems reasonable to conclude that physics, astronomy, medicine, and all other sciences dealing with things that have complex structures are doubtful; while arithmetic, geometry and other studies of the simplest and most general things—whether they really exist in nature or not—contain something certain and indubitable. For whether I am awake or asleep, two plus three makes five, and a square has only four sides. It seems impossible to suspect that such obvious truths might be false.

 

A Deceptive God?

Belief and the Will

An Evil Demon

In response to the objection raised above, Descartes considers his most radical claim yet: it's possible that God -- since God is all-powerful -- is deceiving him about everything, including math

However, I have for many years been sure that there is an all-powerful God who made me to be the sort of creature that I am. How do I know that he hasn’t brought it about that there is no earth, no sky, nothing that takes up space, no shape, no size, no place, while making sure that all these things appear to me to exist?

Some people would deny the existence of such a powerful God rather than believe that everything else is uncertain. Let us grant them—for purposes of argument—that there is no God, and theology is fiction. On their view, then, I am a product of fate or chance or a long chain of causes and effects. But the less powerful they make my original cause, the more likely it is that I am so imperfect as to be deceived all the time—because deception and error seem to be imperfections.

 

Having no answer to these arguments, I am driven back to the position that doubts can properly be raised about any of my former beliefs. I don’t reach this conclusion in a flippant or casual manner, but on the basis of powerful and well thought-out reasons. So in future, if I want to discover any certainty, I must withhold my assent from these former beliefs just as carefully as I withhold it from obvious falsehoods.

At this point, Descartes finds himself with a problem. Despite having what he takes to be good skeptical arguments, he finds himself lapsing back into his old habit of believing the deliverances of his senses....

It isn’t enough merely to have noticed this, though; I must make an effort to remember it. My old familiar opinions keep coming back, and against my will they capture my belief. It is as though they had a right to a place in my belief-system as a result of long occupation and the law of custom. These habitual opinions of mine are indeed highly probable; although they are in a sense doubtful, as I have shown, it is more reasonable to believe than to deny them. But if I go on viewing them in that light I shall never get out of the habit of confidently assenting to them. To conquer that habit, therefore, I had better switch right around and pretend (for a while) that these former opinions of mine are utterly false and imaginary. I shall do this until I have something to counter-balance the weight of old opinion, and the distorting influence of habit no longer prevents me from judging correctly.

But this strategy raises an even bigger problem: many philosophers think beliefs are not the sort of thing that we can just control at will. To illustrate: try believing (right now) that there's a million dollars in your bank account. Chances are, you couldn't do it. You may have entertained the proposition "There's $1,000,000 in my account," but merely entertaining a proposition is not sufficient for belief. In addition to this, Descartes faces an even bigger problem: he was writing at a time when it when it was unthinkable to call God's existence into question. By writing about a "deceptive God," Descartes risked being discredited as a scholar. His solution to both of these problems is somewhat ingenious...

So I shall suppose that some malicious, powerful, cunning demon has done all he can to deceive me—rather than this being done by God, who is supremely good and the source of truth. I shall think that the sky, the air, the earth, colors, shapes, sounds and all external things are merely dreams that the demon has contrived as traps for my judgment. I shall consider myself as having no hands or eyes, or flesh, or blood or senses, but as having falsely believed that I had all these things. I shall stubbornly persist in this train of thought; and even if I can’t learn any truth, I shall at least do what I can do, which is to be on my guard against accepting any falsehoods, so that the deceiver—however powerful and cunning he may be—will be unable to affect me in the slightest. This will be hard work, though, and a kind of laziness pulls me back into my old ways. Like a prisoner who dreams that he is free, starts to suspect that it is merely a dream, and wants to go on dreaming rather than waking up, so I am content to slide back into my old opinions; I fear being shaken out of them because I am afraid that my peaceful sleep may be followed by hard labour when I wake, and that I shall have to struggle not in the light but in the imprisoning darkness of the problems I have raised.

 

God, Belief, and Evil Demons

Summary & Conclusion:

Descartes on Knowledge

Beliefs

Truths

Knowledge

Descartes focused on the question: under what circumstances are our beliefs justified or rational? Nowadays, there is a whole branch of philosophy devoted to this question called "epistemology." One of his great contributions to this field was to model a philosophical method -- radical skeptical doubt -- that many have thought is the ultimate test you could subject your beliefs to. If you'd like to read the rest of the Meditations, to see whether and how Descartes thinks we can ultimately move beyond skepticism in order to provide our beliefs with a certain rational foundation, you can find a copy of it here.

Created by Paul Blaschko and Meghan Sullivan, 2016

For more information, visit the website for God and the Good Life