Your argument doesn't hold up. Whether you observe or can be observed is a question of whether or not you exist. But since your responses are being observed, you exist. And that's where it all ties together. My proof only works when both you and I exist. But I have already proven that we both exist. I know you exist because I can apply the same proof that i used above. Since I am certain that I exist, then you must also exist as you are producing words that I'm observing. If either of us did not exist, this conversation would be impossible as responses would not be made. By proving my own existence, I have proved yours as well, affirming my existence once again and so on... But all that aside, if [b]you[/b] don't know whether or not [b]you[/b] exist, then no amount of logic will help you...