A fair question. Indeed, a host of fair questions. For there are many ways to be puzzled about ethics, and few easy answers. Some examples:

Moral claims are often made as if they possessed a kind of objectivity – as something more than personal or partisan preferences. But where in the world can we find anything like objective values or principles to back this up? Even when we disagree morally, we typically act as if there were something at stake, something to be right or wrong about. And those who argue that moral principles are “cultural” or “relative” typically are on their way to making a case for tolerance, understanding, cooperation, fairness – but this itself looks like a moral view. What is the meaning of moral terms, and what sort of objectivity, if any, does it commit us to? And, if there is such a commitment, can we identify properties of moral practice, or values in the world, that would vindicate it? This is one family of questions.

The objectivity of ethics, it seems, would have to be different from the objectivity of science. Morality gives practical guidance – it purports to say not how things are, but how they ought to be, or how it would be good for them to be. This guidance, moreover, claims to be rational – moral concerns present themselves as good reasons for action, reasons serious enough to outweigh or even cancel certain other pressing concerns or interests.