In what now seems like the prehistoric times of computer history, the early post-war era, there was a quite widespread concern that computers would take over the world from man one day. Already today, less than forty years later, as computers are relieving us of more and more of the routine tasks in business and in our personal lives, we are faced with a less dramatic but also less foreseen problem. People tend to be over-trusting of computers and reluctant to challenge their authority. Indeed, they behave as if they were hardly aware that wrong buttons may be pushed, or that a computer may simply malfunction. Obviously, there would be no point in investing in a computer if you had to check all its answers. But people should also rely on their own internal computer s and check the machine when they have the feeling that something has gone wrong. Questioning and routine double checks must continue to be as much a part of good business as they were in pre-computer days. Maybe each computer should come with the following warning: for all the help this computer may provide, it should not be seen as a substitute for fundamental thinking and reasoning skills.