FIRST Descarte has had dreams where he dreamt that he was awake. From this he concludes that when he’s dreaming he is not in a good epistemic position to say wether or not he is dreaming or awake.
SECOND and even more significant is what follows; namely if he cannot discern wether or not he is dreaming or awake while he is dreaming then it is possible that he cannot know if he is in fact awake.
This movement of Descartes’ is from a claim of the form:
1. One cannot tell if she is in an epistemologically bad situation when she is in such a situation.
2. Even if one percieved to be in a good epistemological position she still cannot know if she is or is not in a bad epistemological position.
The question is wether or not this is a valid form. For example, if the bad situation is blindness; is it not difficult to determine blindness? After all it could be the case that its pitch dark and one is not blind at all. Does it then follow from the idea that its difficult to determine blindness to the idea that if one was sighted it would be difficult to determine if she was sighted. If one was sighted she may be able to see which would confirm that she was sighted. The same is the case in drunkeness. Just because it is dificult for one to determine if she is sober when she is drunk does not mean she will find the same difficulty determing if she is drunk when she is in fact sober. Thus people who are in a bad epistemic situation do not know they are. However on the reverse people in the good epistemic situation can know they are in a good situation through clear headed experiences.
However, Descartes wants argue that wether or not a person is in a bad situation or a good situation they still cannot discern their present situation.
First, Descartes considers the hypothesis that he can know he is not dreaming:
“…at the moment my eyes are certainly wide awake when I look at this piece of paper; I shake my head and it is not asleep; as I stretch out and feel my hand I do so deliberately, and I know what I am doing. All this would not happen with such distinctness to someone asleep.
Indeed! As if I did not remember other occasions when I have been tricked by exactly similar thoughts while asleep! As I think about it more carefully, I see plainly that there are never any sure signs by means of which being awake can be distinguished from being asleep.”
The argument that Descartes is advancing is that no matter how much one believes she is awake it is still possible that she is dreaming. However, this does not seem to follow in my blindness example. For the sake of Descartes argument he is maintaining that there are no experiences one could have when she is awake only; any experience she might have could be dreamt. Even if a test was applied the results themselves could be dreamt. This is why Descartes believes that one can never say wether or not they are dreaming.
If it is true that one cannot discern wether or not she is dreaming then is it possible for her to know anything about the external world based on her sensory experience? Descartes would say no; in order for sensory experience to be valid one must know that she is not dreaming her experiences. This is the skeptics argument.