In Meditations II Descartes argues that even if the Evil Demon is deceiving him about everything else, it cannot be deceiving him about one thing - that he exists. As long as he is doubting everything, he is thinking, and as long as he is thinking, he must exist. Cogito, ergo sum. I think, therefore I am; or: I am thinking, therefore I exist. If the demon tricked him into thinking he didn't really exist, he could reason his way out of the trickery, for if he is doubting his own existence, he is surely thinking. Something is thinking, and that which thinks is the "I".
Clearly, Descartes is making the assumption that thoughts require a subject to think them, something that isn't itself a thought but which in some sense is aware of the thoughts. Is he entitled to assume that thoughts require a thinker? If we think he isn't then his argument fails, for all he'd be left with is "There are thoughts". In any case, he does seem to be assuming that the subject of the thoughts is a continuing thing, subsisting from one thought to the next, and from one kind of mental process to the next (doubting, imagining, etc). He is not entitled to do this, for this could be an illusion created by the demon. But without this continuing "I", his argument looks much weaker: a fleeting "I" that exists only momentarily, as each separate thought occurs, would not be able to reason. It could not form the cogito argument, nor be the subject of clear and distinct ideas, for it would not be able to linger on them long enough to check they really are clear and distinct.
Perhaps you disagree with me, or have your own arguments against Descartes. Get posting!
Tuesday 22 September 2009
The Method of Doubt and Its Purpose
Descartes begins by adopting the position of a global sceptic. He wants to doubt everything because he wants to get back to the foundations of all knowledge in order to build science up from principles that are absolutely certain. He needs to doubt all his previous beliefs because he suspects that some of them are false; if some are, all might be, and therefore all subsequent beliefs would by insecure. He thinks that knowledge has to be certain, indubitable. He sets the standards for knowledge very high - perhaps too high, certainly for everyday purposes, but he is interested in the foundations of scientific knowledge, so perhaps it is reasonable to set very high standards. However, he doesn't live up to those standards himself. Before long he is trusting any ideas that are "clear and distinct", which is not the same as ideas that are indubitable.
Also, Descartes seems to confuse certainty with conviction. Just because you have a strong conviction that a belief is true, it doesn't follow that it is certainly true. He thinks certainty can come from a kind of rational insight (clear and distinct ideas), but this is different from an idea being logically certain.
Descartes' doubt is universal. He is questioning all his beliefs, not individually but by questioning the principles they rest on. For example, any belief based on trusting perception is undermined by the first wave of doubt. It is hyperbolic: extreme, over-the-top, absurd (eg the Evil Demon) - but it has to be like this because it has to get into all the corners of his usual ways of thinking.He must not allow himself to slip back into his habitual attitudes.
First Wave: Doubting the Senses
In the past Descartes has been deceived by his senses. Distant things appear small, for example. However, such perceptual illusions don't undermine all perceptions, he says. They aren't usual (they wouldn't be illusions if they were), and they can often be explained. In fact, Descartes could perhaps have gone further. There are good reasons for doubting all our perceptions in so far as we cannot be sure that the actual world is as it appears to be to us (but this point concedes that there is an actual world distinct from our perceptions).
Second Wave: The Argument from Dreaming
Descartes is a man, so he sleeps and has dreams. Sometimes his dreams are ordinary, sometimes extraordinary. But "there are no conclusive signs by means of which one can distinguish clearly between being awake and being asleep". So, how can he be sure that what he takes to be the real world, when he is awake, isn't actually a dream? He could be dreaming that he is sitting by the fire in his dressing gown, holding a piece of paper.
One response to this is that genuine perception is more coherent than dreams are and that we can usually tell when we are awake and when dreaming; but of course we could simply be dreaming that we can tell the difference! Another response is that the concept of dreaming depends on the concept of real perception, just as the concept of fake money depends on there being genuine money. If everything was a dream, would we be able to talk about dreams and reality? Personally, I think we could, because we would be dreaming that there was a dream world (within the dream-reality) and a "real" world (also within the dream-reality), so I think we could still have versions of the two concepts. Also, Descartes doesn't really need to prove that everything is or could be a dream, only that we can't know when we are dreaming and when we are awake. It is the correct application of the concepts that he is sceptical about.
But dreaming doesn't undermine all Descartes' beliefs. Even in dreams a square has four sides, 2+3 = 5, etc. So he introduces his secret weapon.
The Third Wave: The Evil Demon
What if our minds were controlled by a powerful and malignant demon who wants to deceive us about everything? Then everything would be thrown into doubt. I couldn't be sure anything I experience or think is real. The demon controls all my experience, perceptions, thoughts. He could be deceiving me even about mathematics and geometry, and about apparent features of objects such as shape, location and extension.
So Descartes now doubts everything. But somehow he has to get out of this global scepticism in order to establish a firm foundation for knowledge, but how? He has dug himself a deep hole!At present he does not know a single thing.
Also, Descartes seems to confuse certainty with conviction. Just because you have a strong conviction that a belief is true, it doesn't follow that it is certainly true. He thinks certainty can come from a kind of rational insight (clear and distinct ideas), but this is different from an idea being logically certain.
Descartes' doubt is universal. He is questioning all his beliefs, not individually but by questioning the principles they rest on. For example, any belief based on trusting perception is undermined by the first wave of doubt. It is hyperbolic: extreme, over-the-top, absurd (eg the Evil Demon) - but it has to be like this because it has to get into all the corners of his usual ways of thinking.He must not allow himself to slip back into his habitual attitudes.
First Wave: Doubting the Senses
In the past Descartes has been deceived by his senses. Distant things appear small, for example. However, such perceptual illusions don't undermine all perceptions, he says. They aren't usual (they wouldn't be illusions if they were), and they can often be explained. In fact, Descartes could perhaps have gone further. There are good reasons for doubting all our perceptions in so far as we cannot be sure that the actual world is as it appears to be to us (but this point concedes that there is an actual world distinct from our perceptions).
Second Wave: The Argument from Dreaming
Descartes is a man, so he sleeps and has dreams. Sometimes his dreams are ordinary, sometimes extraordinary. But "there are no conclusive signs by means of which one can distinguish clearly between being awake and being asleep". So, how can he be sure that what he takes to be the real world, when he is awake, isn't actually a dream? He could be dreaming that he is sitting by the fire in his dressing gown, holding a piece of paper.
One response to this is that genuine perception is more coherent than dreams are and that we can usually tell when we are awake and when dreaming; but of course we could simply be dreaming that we can tell the difference! Another response is that the concept of dreaming depends on the concept of real perception, just as the concept of fake money depends on there being genuine money. If everything was a dream, would we be able to talk about dreams and reality? Personally, I think we could, because we would be dreaming that there was a dream world (within the dream-reality) and a "real" world (also within the dream-reality), so I think we could still have versions of the two concepts. Also, Descartes doesn't really need to prove that everything is or could be a dream, only that we can't know when we are dreaming and when we are awake. It is the correct application of the concepts that he is sceptical about.
But dreaming doesn't undermine all Descartes' beliefs. Even in dreams a square has four sides, 2+3 = 5, etc. So he introduces his secret weapon.
The Third Wave: The Evil Demon
What if our minds were controlled by a powerful and malignant demon who wants to deceive us about everything? Then everything would be thrown into doubt. I couldn't be sure anything I experience or think is real. The demon controls all my experience, perceptions, thoughts. He could be deceiving me even about mathematics and geometry, and about apparent features of objects such as shape, location and extension.
So Descartes now doubts everything. But somehow he has to get out of this global scepticism in order to establish a firm foundation for knowledge, but how? He has dug himself a deep hole!At present he does not know a single thing.
Wednesday 16 September 2009
Matrix
I have never seen the Matrix before (shock horror) but i am fairly sure this is a good example of what to expect - watch out for something in this video that Graeme shall surely be saying in a lesson soon...
Link: http://www.youtube.com/watch?v=cJDrpJhTycs
(having trouble with the link, so either click on post name or copy and paste link to browser)
Link: http://www.youtube.com/watch?v=cJDrpJhTycs
(having trouble with the link, so either click on post name or copy and paste link to browser)
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