Something to Think About

One day, a man named Garrett decided to swing with his eyes closed while thinking.  During this time of intense brain activity, he imagined that the tree that we see above ground is only the roots, and that the real tree which houses most of the life of the world is underground in the roots, which we've never bothered to dig up and check out.  This put me in a philosophical mood today.  What if nothing is as it seems?  I'm not talking hypothetical, but if everything humans have figured out by themselves is wrong.  Since we base new facts on old ones, it's entirely possible.  If we were even slightly wrong on the original observations, it throws off the rest of the facts we've ever thought to have "known".  How crazy is that?