Imagine a group of men have lived their whole life inside a cave, tied up and facing the back wall. They have a fire behind them, so the only things that they can see are the shadows of objects and people who go through the fire. If one of the "prisioners" were set free, he would realize that the shadows are just an inferior representation of the said objects, right?
But. If the objects are more real than the shadows; how do we know there is not something more real than the objects we see? Is there an ultimate reality?