First: Consider the skeptic's charge that we can never be confident about the reliability of our normal sources of knowledge (i.e., perception, memory, introspection, and reasoning). Does it follow from the fact that we are sometimes mistaken when we rely on these sources that we are always mistaken? Do you agree with Descartes (and skeptics) that only propositions that are beyond all doubt can be knowledge? How would you argue against this view?
Second: Is there any way you can tell whether you are awake or dreaming? Is Descartes right that he can't tell the difference? Can you tell whether an evil genius is systematically deceiving you? Why or why not?