Charlie's brush with mortality left him with a brain altered by the ether.
I think he was born with an altered brain. He loves playing the roll of an intellectual, but he lacks the intellect to pull it off. He an Al Gore are a good pair...neither are what they would like the public to believe they are. Their dialogue proves that Rose is no intellectual, and Gore doesn't know squat about "Global Warming" or any other subject...he was born with a deficient brain.