utilitarianism

Less Wrong: Ethics as a black box function

The Ancient Greek concept of happiness was significantly different from the modern concept of happiness. It tended to be rather teleological and prescriptive rather than being individualistic. You achieved "true happiness" because you lived correctly; the correct way to live was not defined based on the happiness you got out of it. There were some philosophers who touched on beliefs closer to utilitarianism, but it was never close to main stream. Epicurus, for example, but his concept was a long way from Bentham's utilitarianism. The idea that happiness was the ultimate human good and that more total happiness was unequivocally and absolutely better was not even close to a mainstream concept until the enlightenment.

Oh, some of Socrates' fake debate opponents did argue pleasure as the ultimate good. This was generally answered with the argument that true pleasure would require certain things, so that the pursuit of pure pleasure actually didn't give one the most amount of pleasure. This concept has objectionable objective, teleological, and non-falsifiable properties; it is a very long way from the utilitarian advocacy of the pursuit of pleasure, because its definition of pleasure is so constrained.

Much of ethics prior to the enlightenment dealt more with duties and following rules.

Virtue ethics was generally about following rules. Duty was not the primary motivator, but if you did not do things you were obliged to do, like obey your liege, your father, the church, etc., you were not virtuous. Most of society was, and in many ways still is, run by people slavishly adhering to social customs irrespective of their individual or collective utilitarian value.

I did not claim that everyone operated explicitly off of a Kantian belief that duty was the ultimate good. I am simply pointing out that most people's ethical systems were, in practice, simply based on obeying those society said should be obeyed and following rules society said they should follow. I don't think this is particularly controversial, and that people can operate off of such systems shows that one need not be utilitarian to make moral judgements.