Descartes - stages of doubt

Week two's topic is knowledge (continues for week three also) and we start by reading chapter 1 of  Blackburn and then Chapters 1 and 2 of Guttenplan et al. The first set task was not particularly enlightening so our tutor has set some alternative questions. My initial thoughts are as follows:

(i) Examine the various stages of doubt in Descartes' full argument. Say whether you think each stage or kind of doubt is a reasonable one.
(ii) if you think it is reasonable, support your position with examples and an argument.
(ii) if you think it is unreasonable, support your position with counter-examples and an argument.

Firstly, Descartes states that as a child he believed things which have subsequently been shown to be untrue - this establishes the possibility that so-called knowledge may be based on unsound foundations.

Descartes then explains that it is not possible to doubt everything, but this is not necessary, he only needs to establish that some things cannot be known for certain to call into question some fundamental beliefs. Unless something is "completely certain and indubitable" it can be doubted.
Next, Descartes explores what, if anything, we can know that cannot be doubted. He does this by introducing a number of possible reasons why we might think that some beliefs are not completely certain and indubitable. The steps are:

1. We are sometimes deceived by our senses therefore we cannot be sure that we are not being deceived at any particular time.
I think this is a flawed argument. Whilst it is true that at any one time we may be deceived by our senses, i.e. under an illusion or misapprehension, in the vast majority of these cases we subsequently understand what leads to the illusion or misapprehension. So for me, this argument fails on a metaphysical level. If I sense something that is 'impossible', i.e. does not accord with my understanding of the world, then I don't really believe it is true, i.e. I am not 'taken in' and I believe that there must be a rational explanation. Admittedly there are some things which we cannot explain, but this is not the same as accepting that we are actually deceived by our senses and believe things that are 'impossible'.
2. Mad people believe things that are not true
Descartes rejects this argument himself as he is confident that he isn't mad.
3. Dreaming can lead to deceptive experiences and we cannot be sure if we are awake or dreaming at any particular time.
I reject this as a reason for doubting all knowledge since my experience of dreaming is very different from my experience of being awake. When I wake up I can tell the difference.
Nevertheless, the dreaming argument does have a lot of philosophical merit and very neatly challenges our notion of existence. I accept that in the strictest sense we cannot prove that we aren't dreaming at any particular time or even that the whole of life isn't a dream and in this respect the argument is an important step in any serious attempt to enquire into what we know about existence.
My initial reaction however is to say that we have no indication that it is true that everything is just a kind of dream. It seems to be such a remote possibility that it isn't very helpful in understanding the way the world is. Unless Descartes can provide some support for why we should believe that everything is a dream, in the form of a coherent argument that makes sense, then the natural reaction to this argument is to reject it.
4. We cannot rely on God's omnipotence and goodness to ensure that we are not deceived as it is apparent that we are sometimes deceived.
I agree with this. If there is a God then it seems clear that he hasn't arranged things so that we are never deceived or under misapprehensions, at least in the sense that Descartes is using "deceived".
From a personal perspective I don't have the remotest concept of what 'God' could be, so to base any argument on what 'God' does or doesn't do is literally nonsensical.
5. We cannot be sure that a malicious demon is not deceiving us while we are awake.
As with the dreaming argument, I think we can see that logically this has something going for it, but on a personal level I don't believe in malicious demons so I would reject it as being impossible. For me to accept this argument it seems to me that I would need to admit the existence of malicious demons first.

Give your over-all opinion on Descartes' requirement for certainty in order for us to claim that we are justified in believing something about the world.
Do you think he is being reasonable?
Finally, what do you think of the cogito argument?
Whilst I don't think Descartes' arguments in favour of doubting everything are bullet-proof, I do very much admire the philosophical method which he sets out. Descartes' insistence that truth must be certain and indubitable is a valuable yard-stick and his clarity of thought and willingness to 'start from the beginning' is admirable.

I have found this exercise very challenging. Descartes arguments are difficult to reject outright. Although on the whole I tend to reject his conclusions, the method by which he constructs his arguments is clever and not entirely unconvincing.

The cogito marks a major stepping-stone in philosophy. Like many others, I tend to think that Descartes stretches the argument too far. Whilst I accept that "there is thinking going on" is true, the question remains what does Descartes mean by "I".