Utilitarianism, explicitly. (1) You seek the greatest good for the greatest number – “the good” is defined as happiness, but due to the difficulty in measuring the utility of others, “the good” is often effectively defined as preference fulfillment.
(2) We’re just looking forward, not backwards. You don’t keep your promise because you gave your word, you keep it because of the bad consequences that would follow from breaking your word. And if you know you can create more utility by breaking your word, you’re obligated to do so. (Of course, the act of giving your word usually has a strong influence on the consequences of your decision to honor or not honor it.)
(3) Everyone’s happiness counts the same. The serial child molester should figure just as prominently in your calculations as the world’s greatest philanthropist.
I think there are a lot of people who are effectively utilitarians, but who are turned off to being explicitly so by the kind of unrealistic examples that Blaster Master mentioned. Like this:
Sure, you could dream up a hypothetical situation in which it might be best to kill the old man; specifically, in this case, if you knew you could keep it 100% secret, and/or people wouldn’t care if they found out he was murdered. But that’s just not realistic. In the real world, you don’t kill even thoroughly objectionable people because nobody likes to live in a society in which people are murdered. It leads to general misery. Also, you can’t know that nobody in the world likes or cares about him, so you’re dealing with a probability instead of an absolute, and the chance of unforseen suffering has dimished the expected utility of the killing. Similarly, you yourself may be caught and thrown in jail, leading to massive quantities of misery for you and your loved ones.
Essentially the same problems arrise with your shoplifting example, though it is more realistic that such a thing could actually be justifiable.
Not “produce” moral results. They are moral results. Saying that such an outlook could justify killing or stealing, and that killing and stealing are “obviously” immoral, is missing the point. They are not (we think) inherrently moral or immoral. They are one or the other for different, more fundamental reasons.
I can’t speak for all utilitarians, but generally the reason that we choose happiness as the ultimate good is because it is the only thing that is desirable for its own sake. I.e., it is the purest good; any other good can be made bad by circumstance.
(All of this is subjective, incidentally. My moral sytem isn’t “better,” per se, just “preferred.” It’s ultimately based on some arbitrary axioms, like everyone else’s morality. If anyone ever counters my argument by saying “I don’t care about preventing misery,” that would be the end of the rational portion of our debate. I could still make an emotive argument about why he should care, but there would be no logical reason for our disagreement.)