Utilitarianism is a philosophical school of thought that holds that good is whatever reaps the highest 'utility'. What gives us the most safisfaction, be it virtue or pleasure, is what's right. Jeremy Bentham, one of the main thinkers of the English enlightenment came up with this theory, saying that man our existance essentially comes down to two variables: pleasure and pain. From there he posited the theory of utilitarianism; good is bringing happiness to the greatest amount of people. It's a little hedonistic--John Stuart Mill, another utility theorist, basically modified this by putting an emphasis on quality over quantity. The main problem with the theory of utility is that doesn't really line up with our traditional notions of morality or even western liberalism itself. Here's a scenario, the President of the United States and a janitor are both stuck in a sinking boat. You only have the opportunity to save one or the other. The utilitarian would say that you save the President, since he is more important (e.g. saving him would maximize everyone's utility). Good is not really being maximized at this point. Some acts that are beneficial to society at large may not indeed be moral. Slavery and genocide might be seen as good for society at large but it doesn't make it right. It's actually very difficult to assign a preference list when dealing with moral questions--that is fundamental weakeness in this system of ethical thought.