Cogito, ergo sum

Real Harry Potter fans usually know this quotes as well as one's pocket. Harry "dies" and meets Dumblebore at Kings Cross. After a long talk they conclude that Harry is not really dead and he makes the decision to go back to the other world and fight against Voldemort. This is the end of their conversation, and happens just before Harry leaves:

"Tell me one last thing," said Harry. "Is this real? Or has this been happening inside my head?" "Of course it is happening inside your head, Harry, but why on earth should that mean that it is not real."

JK Rowling, Harry Potter and the Deathly Hallows

A French philosopher said something with the same theme:

"Cogito, ergo sum"- I think there fore I am.

René Descartes

He said that this was the only statement that where absolutely true, the other stuff is just speculations that we can't be sure about. Maybe this is the only truth. Life is only pattern with thoughts and it's just happening in our head. Imagine a psychically sick person. In his head things are happening that is not real to us. But to him it's absolutely as real as for us. He can smell the smell, hear the sound, feel the spiders crawling on his skin or his "imaginary" friend is talking to him. But does it really matters? Isn't what we feel and sees more important than what is. If we know there is an flower on the table, but we can' see it or feel it or smell it, does it matters if there is a flower on the table? The only thing that is crushing this philosophy like a glass from a skyscraper is death. If someone shoots us, will we die even if we can't see it or feel it? Probably.