[discussing the Doomsday machine]
President Merkin Muffley: How is it possible for this thing to be triggered automatically and at the same time impossible to untrigger?
Dr. Strangelove: Mr. President, it is not only possible, it is essential. That is the whole idea of this machine, you know. Deterrence is the art of producing in the mind of the enemy... the FEAR to attack. And so, because of the automated and irrevocable decision-making process which rules out human meddling, the Doomsday machine is terrifying and simple to understand... and completely credible and convincing.