I think...Therefore I am
Famous line isn't it. But have you really thought about it?
It's a philosophical proof in a sense. We cannot prove anything without a doubt but or own existence and only that because we can think about it. I won't go into the details of that, primarily because I'm rusty on the philosophy myself.
A similar proof is that there is no specific color that equals red, because every individuals eyes will display color just a little bit different. So we as a society agree that some shade is red, with a high level of variance. But what about those who are color blind. To them red doesn't exist at all. It's simply a shade of gray (or something in that area) that they have been forced to learn as red. But distinguishing between red and blue and green when they are all the same luminosity can be difficult, if not impossible.
The point I'm trying to make is that thinking actually makes reality much more ill-defined. If colors don't exist, because they are simply a construct of an individuals visual perception, how could anything exist? I hate to dive into the popular media philosophy, but our reality could very well be Matrix-like. Our brain requires our five senses to communicate with the outside world. Those senses can fool us and/or be manipulated. Just ask anyone who's taken a hit of LSD.
So who's to say the world we live in is any more real than the world of cyber space or the worlds in our dreams? These are common questions that many people have asked, but I wonder, 'If thinking is required to exist, then animals and/or brain-dead humans don't exist, except in my own mind?'
I believe thinking actually makes your existence even more dubious. Or rather, the world we exist in is.