If you accept that premise then how do you KNOW what really is/isn't?
I know that Je pense donc je suis. Cogito ergo sum.
You think therefore you exist. Allegedly. That doesn't transfer to the larger question. How do you know what else exists besides you apart from you? How do you know that many things may well exist outside your ken and because of your limitations you can never access them? How do you know that what you know is real and not manufactured by you to make your life tolerable livable purposeful?
