One of Asimov's favorite plot devices was to take a particular phobia and apply it to an entire culture. It was fear of the dark in Nightfall, and in Naked Sun it is agoraphobia. Long before the invention of the Internet Asimov wrote about a future society in which everyone communicated by video screens while never leaving their homes. Now a murder has been committed and it could only have been done by someone outdoors, which is unthinkable. Only robots go outdoors and robots are programed never to kill.