I'm taking a philosophy of mind course right now.. This is something that comes up when the sophomores want to derail the professor.
A Greek named Pyrrho or something like that was the first person to record serious doubts of the existance of anything around him. I guess in the end, he was convinced that he was the only thing that existed, and his followers had to constantly protect him from walking into holes and stuff, because he didn't believe that they were real. This is stuff I learned about a few years ago, but I think my recollection is good.
We were talking about Descartes just recently, though. He was around in late Medieval period, and he brought up serious doubts of the reality of the world around him. Sensory information is unrelaiable, but what he was sue of was that he was a thinking beng. That's all he could say for sure at first. cogito ergo sum. I think, therefore I am (exist).