Economic concepts and methods are used to throw light on some aspects of common-sense ethics and the difference between it and Utilitarianism. (1) Very few exceptions are allowed to the rules of common-sense ethics, because of the cost of information required to justify an exception to Conscience and to other people. No such stringency characterizes Utilitarianism, an abstract system constructed by philosophers. (2) Rule Utilitarianism is neither consistent with common-sense ethics, nor does it maximize utility as has been claimed for (...) it. The same is true of more recent variants of Utilitarianism. (3) Second best and first best are usually identical in common-sense ethics. They are often identical in Utilitarianism when a moral situation can be represented by a Prisoner's Dilemma. However, problems arise in permissive forms of Utilitarianism when it is not obvious that second best should be applied. (shrink)