I should probably have put this one first, but I didn't. I actually heard the example once of someone on LSD thinking he could fly and stepping out a window. Because he believed he was flying, he might as well have been, the example went. This is really a perfect example of the other side. No matter what he believed he was doing, he was falling and he died when he hit the ground.
Perception is fallible.
Memory can change. People color their accounts of an event to suit what they believe, or what they want others to believe. None of that changes what is. No matter how many people testify, under oath, that the guy who went out the window hung suspended in mid-air and then flew away, it didn't happen. He still crashed into the ground and died.