When Descartes remembers occasions when he is dreaming, he falsely believes he is awake. Reflecting on this, Descartes thinks he cannot ever tell whether or not he is dreaming. How can he know he perceives his hands right now? Maybe, it is all just a dream. If it were just a dream everything would seem to be the same. In order to have knowledge the suggestion he is dreaming is false, he somehow has to have some knowledge of being awake.
I believe his dream argument could be formed in this way:
1.When we are dreaming we are not in a good position to tell whether we are actually dreaming or awake. 2.Any experience you are having right now could also mean you are dreaming. In other words, you can’t possibly know you are dreaming even if it is a dream. 3a. For each of your experiences, you can’t tell whether your experience is a dream or not. (You can’t tell which of your dreams is a waking experience or a dreaming experience). 3b. For all you know, all of your experiences may be dreams. (You may be walking around in a dream, never having any walking experiences)
Most philosophers think the dream argument supports both conclusions, but many philosophers also think this argument is strong enough to support 3a but not 3b. It is not really clear whether Descartes is arguing for the stronger claim or the weaker claim. It could be 3b, the weaker...