Multivac has problems. It does not respond to commands, and isn’t following its built-in program to self-diagnose the cause. As the global economy depends on Mulitvac, this could result in panic across the world. Teams of technicians have been trying to identify what is wrong for three days. Finally, a scientist discovers the “key item” needed to fix the problem. It is a simple thing that we are all taught to use as children.  Jack Weaver came out of the vitals of Multivac looking utterly worn and disgusted.  From the stool, where the other maintained his own stolid watch, Todd Nemerson said, “Nothing?”  “Nothing,” said Weaver. “Nothing, nothing, nothing. No one can find anything wrong with it.”  “Except that it won’t work, you mean.”  “You’re no help sitting there!”  “I’m thinking.”  “Thinking!” Weaver showed a canine at one side of his mouth.  Nemerson stirred impatiently on his stool. “Why not? There are six teams of computer technologist roaming around in the corridors of Mulitvac. They haven’t come up with anything in three days. Can’t you spare one person to think?”  “It’s not a matter of thinking. We’ve got to look. Somewhere a relay is stuck.”  “It’s not that simple, Jack!”  “Who says it’s simple? You know how many million relays we have there?”  “That doesn’t matter. If it were just a relay, Multivac would have alternate circuits, devices for locating the flaw, and facilities to repair or replace the ailing part. The trouble is, Mulitvac won’t only not answer the original question, it won’t tell us what’s wrong with it… And meanwhile, there’ll be panic in every city if we don’t do something. The world’s economy depends on Mulitvac, and everyone knows that.”  “I know it, too. But what’s there to do?”  “I told you, think. There must be something we’re missing completely. Look, Jack, there isn’t a computer bigwig in a hundred years who hasn’t devoted himself to making Mulitvac more complicated. It can do so much now — it can even talk and listen. It’s practically as complex as the human brain. We can’t understand the human brain, so why should we understand Mulitvac?”  “Aw, come on. Next you’ll be saying Multivac is human.”