Sherlock Holmes and Dr Watson are going camping. They pitch their tent under the stars and go to sleep. In the middle of the night Holmes wakes Watson up: "Watson, look up at the stars, and tell me what you deduce."
Watson: "I see millions of stars and even if a few of those have planets, it's quite likely there are some planets like Earth, and if there are a few planets like Earth out there, there might also be life."
Holmes: "Watson, you idiot, somebody's stolen our tent!"