"We tried arguing with them. Their point was that a human being in a gamma field was endangering his life and that it didn’t matter that he could remain there half an hour safely. Supposing, they would say, he forgot and remained an hour. They couldn’t take chances. We pointed out that they were risking their lives on a wild off-chance. But self-preservation is only the Third Law of Robotics—and the First Law of human safety came first. We gave them orders; we ordered them strictly and harshly to remain out of gamma fields at whatever cost. But obedience is only the Second Law of Robotics—and the First Law of human safety came first. Dr. Calvin, we either had to do without robots, or do something about the First Law—and we made our choice."