My work lately has lead me to think there are two parts to the "self", the intelligence and the simulation running around it within the brain. The intelligence uses the senses to better augment the simulation to represent external reality. Sometimes I think that leads us to believe that reality isn't "real" but this is just the limit of our perceptual self. When our internal simulation gets a bit off or were poke at its resolution too much we notice the gaps, and this leads some people to erroneously declare their is no reality when I think in fact they are just poking holes in their own cognitive model. Ones flaws does not reject the others existence.

When you drill into this concept is goes a long ways in describing everything from Platos cave to this guys hunches.

It also opens up some interesting possibilities that our intelligence could but remote in some fashion while we still perceive ourselves within our body... Or lots of other things.

All in all though I think our social nature is used to validate our internal simulations. Just the fact that other intelligences are creating similar models leads me to think there is an objective reality.