Descartes' Meditations: 1 & 2

1. In the First and Second Meditations Descartes attempts to show that his various empirical and mathematical knowledge-claims are insufficiently grounded. A crucial role in this is played by the argument from dreaming.

How would you evaluate the Dream argument after outlining it?

Issues I don't understand too well:

Does Descartes’ (clearly correct) observation about the fallibility of sense experience really show that there is something lacking or dubious about knowledge-claims based on sense experience?

Does the fact that such knowledge-claims are fallible really mean that they are dubitable?

That is, can I really ‘doubt’ that I have a hand when I am perceiving my hand under conditions I believe to be optimal? (Recall that the reason why Descartes introduces the argument from dreaming lies in the point he is making about when he says that he would be insane, i.e., irrational were he to doubt sense experience when this is had under certain, ‘normal’, i.e., optimal conditions.)

What crucial assumption underpins the argument from dreaming and indeed the subsequent argument concerning the possibility of an evil spirit who is radically deceiving him?

Also, in the second line of the question, i thought tht descartes beleived in mathematical knowledge claims and that they were suffieciently grounded??