“Just before Giskard’s end, he conceived of a robotic law that superseded even the first. We called it the ‘Zeroth Law’ out of an inability to think of any other name that made sense. The Zeroth Law is: ‘A robot may not injure humanity or, through inaction, allow humanity to come to harm.’ This automatically means that the First Law must be modified to be: ‘A robot may not injure a human being, or, through inaction, allow a human being to come to harm, except where that would conflict with the Zeroth Law.’ And similar modifications must be made in the Second and Third Laws.”