It's pointless whether to debate it or not; 1. it's impossible to know. 2. either way you wont change your actions. 3. if it is considered all it does is make reality depressing.
It's not impossible to know as long as we know stuff, and as long as there is stuff that we know. Descartes argument was that we can practice doubt to the point where we can doubt everything, but we cannot doubt that thing that is
doing 'doubt'. It is untouchable by any concept that it must be used to practice. That also works for knowing,
doing 'know', and that thing that is
doing 'know' is untouchable by the practice of it. If one can be said to know anything--anything at all, like for instance that one's untouchable self is the only sure thing--then one can also be said to know other things just as well. There's no real difference between knowing there's an untouchable self and knowing that you are hungry or that bachelors are men.
The idea that knowledge of the world "out there" is unassailable is based off the model that has a mind separate from the world, looking at the world and getting to know it essentially from afar, from outside it. It is a mind uncovering the truth of a remotely objective world through discovery. If you don't buy into that model, solipsism goes *poof*.
I think the world is what you make it though, but I'd personally prefer to look at the world without considering it
Good! This is a much more interesting approach: a mind that engages the world rather than sits around wondering about it without realizing that it is the world sitting around wondering about itself. The mind that literally is the world--no distinction to be made that separates them at all--is the mind engaged in being.