Berkeleys Laws: (1) The world is more complicated than most of our theories make it out to be. (2) Ignorance is no excuse. (3) Never decide to buy something while listening to the salesman. (4) Most problems have either many answers or no answer. Only a few problems have a single answer. (5) Most general statements are false, including this one. (6) An exception – test a rule; it never proves it. (7) The moment you have worked out an answer, start checking it; it probably isnt right. (8) If there is an opportunity to make a mistake, sooner or later the mistake will be made. (9) Check the answer you have worked out once more – before you tell anybody. – Edmund C. Berkeley