Russell's teapot is a philosophical device named for 20th century philosopher Bertrand Russell. It demonstrates the futility of proving a negative proposition. Russell asserted, in a strictly hypothetical sense, that a teapot might be orbiting the sun between Earth and Mars. He asserted that it was too small to be detected, and then asked how he could be proven wrong.
Bertrand Russell developed what became known as the "celestial teapot" argument in a 1952 essay, "Is There a God?" that was intended for, but refused publication by, Illustrated magazine. His intent was to shift the burden of evidence away from himself and his fellow atheists by showing that no argument could ever, even in theory, disprove the existence of an immaterial, supernatural god. Rather, as he went on to argue in the essay, the burden of proof rests with those who make the positive assertion that a god of some kind does exist. In terms of his teapot analogy, it is not the duty of nonbelievers in the celestial teapot to prove that it does not exist, but the obligation of teapot believers to demonstrate good evidence for its existence. Later variations of the celestial teapot device include Carl Sagan's invisible dragon, the Invisible Pink Unicorn and the Flying Spaghetti Monster.