Are you sure you see the reality out there? That is the question. The brain does not receive an image like a camera does. The brain is not a passive processor. What you see is constructed in the brain. How do you see with your brain?
Where does your body end? All fairly clear to you, but not to your brain. A tool you hold in your hand is a part of your body, and sometimes a rubber hand can seem like your real hand. How can this be?