- The Mysterious Stranger, and Other Stories by Mark Twain (gutenberg.org)
It was in 1590—winter. Austria was far away from the world, and asleep; it was still the Middle Ages in Austria, and promised to remain so forever. Some even set it away back centuries upon centuries and said that by the mental and spiritual clock it was still the Age of Belief in Austria. But they meant it as a compliment, not a slur, and it was so taken, and we were all proud of it. I remember it well, although I was only a boy; and I remember, too, the pleasure it gave me.
- Dream argument (Wikipedia)
The dream argument is the postulation that the act of dreaming provides preliminary evidence that the senses we trust to distinguish reality from illusion should not be fully trusted, and therefore, any state that is dependent on our senses should at the very least be carefully examined and rigorously tested to determine whether it is in fact reality.