Why does descartes doubt everything

In his Third Mediation, Descartes tries to overcome this clash of perspectives, and the self-doubt it provokes, by proving that God cannot be a deceiver. But this introduces a new clash between theology and experience: a good God would not cause him to make mistakes, and yet he knows for certain that he has often gone wrong. In the Fourth Meditation, Descartes resolves this conflict by appealing to free will. God has given him perfect cognitive equipment. But how he uses it is up him, and he often uses it incorrectly.

Instead of waiting for clear and distinct evidence to come in, he goes ahead and believes things that are uncertain. No wonder he is often wrong. This solution raises lots of questions. Can we really decide whether to believe something? I Things are not always just as they seem at first glance or at first hearing, etc.

But then, Descartes argued, it is prudent never wholly to trust in the truth of what we perceive. In ordinary life, of course, we adjust for mistaken perceptions by reference to correct perceptions. But since we cannot be sure at first which cases are veridical and which are not, it is possible if not always feasible to doubt any particular bit of apparent sensory knowledge. Second, Descartes raised a more systematic method for doubting the legitimacy of all sensory perception. On this supposition, it is possible to doubt that any physical thing really exists, that there is an external world at all.

Severe as it is, this level of doubt is not utterly comprehensive, since the truths of mathematics and the content of simple natures remain unaffected. Even if there is no material world and thus, even in my dreams two plus three makes five and red looks red to me. In order to doubt the veracity of such fundamental beliefs, I must extend the method of doubting even more hyperbolically. Finally, then, Descartes raised even more comprehensive doubts by inviting us to consider a radical hypothesis derived from one of our most treasured traditional beliefs.

What if there is an omnipotent god, but that deity devotes its full attention to deceiving me? I The problem here is not merely that I might be forced by god to believe something that is in fact false; Descartes meant to raise the far more devastating possibility that whenever I believe anything, even if it has always been true up until now, a truly omnipotent deceiver could at that very moment choose to change the world so as to render my belief false. On this supposition, it seems possible to doubt the truth of absolutely anything I might come to believe.

Although the hypothesis of a deceiving god best serves the logical structure of the Meditations as a whole, Descartes offered two alternative versions of the hypothetical doubt for the benefit of those who might take offense at even a counter-factual suggestion of impiety. It may seem more palatable to the devout to consider the possibility that I systematically deceive myself or that there is some evil demon who perpetually tortures me with my own error.

So if you are looking for a solid foundation for knowledge, perception is the place to start. We might be deceived about the beliefs we learn from other people or any beliefs that require a great deal of reasoning. But our eyes don't usually lie to us about our surroundings. And we need well-functioning senses in order to conduct scientific observations -- the Enlightenment gold standard for being rational.

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.

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!

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! Here Descartes introduces a theme explored in many science fiction films.

For example, Inception:. Is the argument valid? Think of counterexamples. We will discuss these in class. 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.

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. 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.

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 his senses 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. 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. The doubting is initiated in two stages. In the first stage, all the beliefs we have ever received from sensory perceptions are called into doubt. In the second stage, even our intellectual beliefs are called into doubt.

Descartes presents two reasons for doubting that our sensory perceptions tell us the truth. First of all, our senses have been known to deceive us. Examples of the sort of systematic deception he has in mind here include phenomena such as the bent appearance of a straight stick when viewed in water and the optical illusion of smallness created by distance.

The second doubt that Descartes brings to bear on sensory perceptions is more dramatic. Descartes claims that even in optimal viewing conditions i.