Except we do not fully understand dreams. We can not fully control them. We hardly understand all the workings of the human brain. To say we could control hallucinations and dreams as easy as controlling what you say when wide awake is quite a claim. I don't know about you, but most my dreams are out of my control. So, to say that your working in an unpredictable manner is proof of your existence is false. I can not determine what I dream about at all when I enter sleep.