"Nothing exists; all is a dream. God - man - the world - the sun, the moon, the wilderness of stars - a dream, all a dream; they have no existence. Nothing exists save empty space - and you!"
“And you are not you - you have no body, no blood, no bones, you are but a thought. I myself have no existence; I am but a dream - your dream, creature of your imagination. In a moment you will have realized this, then you will banish me from your visions and I shall dissolve into the nothingness out of which you made me …
“I am perishing already - I am failing - I am passing away. In a little while you will be alone in shoreless space, to wander its limitless solitudes without friend or comrade forever - for you will remain a thought, the only existent thought, and by your nature inextinguishable, indestructible. But I, your poor servant, have revealed you to yourself and set you free. Dream other dreams, and better!
“It is true, that which I have revealed to you; there is no God, no universe, no human race, no earthly life, no heaven, no hell. It is all a dream - a grotesque and foolish dream. Nothing exists but you. And you are but a thought - a vagrant thought, a useless thought, a homeless thought, wandering forlorn among the empty eternities!”
He vanished, and left me appalled; for I knew, and realized, that all he had said was true.”
Mark Twain - The Mysterious Stranger
The terrifying claymation version here.