There's the idea that the world is a simulation. I believe it is, but not in the "Matrix" kind of way - more that everything you perceive and experience is a "model" of the outside world that your brain has constructed from the various input signals.

You only see a partial reconstruction, a projection of the outside world, literally Plato's cave (the cave being the skull). Sometimes things come in from outside (what you see etc) but most activity is internal.