Leave an electric hair clipper at a visible spot. If the device disappears, then you know it's true.
"If we take in our hand any volume — of divinity or school metaphysics, for instance — let us ask, Does it contain any abstract reasoning about quantity or number? No. Does it contain any experiential reasoning about matters of fact and existence? No. Then throw it in the fire, for it can contain nothing but sophistry and illusion." ― D. Hume
28/03/2016: Not motivated to post anymore after the umpteenth purge since my registration.