The Nature of Reality

I was recently reading a piece of literature called The Meditations by a philosopher named Rene Descartes in which he methodically questioned, analyzed, and proved real the things around him, from his own existence, to God, to the entire world around him. This got me thinking once again about how I define reality, and even what reality is. How can I ever really presume to know anything for sure? This painting was the result of my contemplation.