Brain mirage

How do we know we exist? That is a very good question. Not even saying that the matter is present can you tell that it is a mirage or not. Is it because of the brain? Or are there other reasons we cannot tell things exist. Noone can prove that objects are anywhere. We could live in a world where everything is made up of everything. How do we know what the sense of touch is? Because we can feel things? Or is it mental scheme? That would be awesome wouldnt it. Why is the world as we "see" it the way it is, does it have to do something with the brain?
The brain is very powerful if you believe it or not. Noone yet has been able to unlock it potential, and lets hope noone does.