What You Believe Is What You Get

You must have heard or read somewhere: " Everything is an illusion; Nothing is real; The material world is just an imagination of our mind". There's a famous statement: ' If a leaf falls from a tree in a forest, but no one is there to see it, then it must have not fallen'. So is the universe just a deception to our senses? We all see the things around us only because we believe they are there!!
Or does our belief only create the material things ?

This is really a scientific theory, I think something called subconscious mind. So the same theory can also be applied to the existence of god. For those persons who believe god exists, he really does; and for those who don't believe in his existence, he doesn't exist. May be that's why we are never able to prove the existence or non- existence of god. That's how there can be a difference between the spiritual lives of people. : O