How much do you know about reality, really?

Well, I know that the term “electricity” has become so overly broad as to be nearly meaningless.

Check this out:
http://www.amasci.com/miscon/whatis.html

I also know that Descartes gives me a headache.

Though I am 18.

I don’t really read that classical philosophical reading material. Their theories clash too much with my perception.

So what does it mean to “know” something? I think you’re correct, that it’s very difficult to have absolute knowledge (although I think that mathematicians and others who play with formal systems do have it). On the other hand, I have functional hypotheses that allow me to walk, talk, and function in society. That’s knowledge, although not absolute.