Ethics is the science that studies what humans should do in the various circumstances in which they find themselves.

When ethics poses this question in a general way – not concerning itself with particular cases – it's called general or theoretical ethics. When it seeks to understand how a general ethical law, once established, should be applied in particular situations, it's called particular, applied, or practical ethics.

The former is a pure science, whereas the latter is both a science and an art – thus paralleling the distinction between general and applied logic. Insofar as either ethics or logic is concerned with abstract and general laws, the term “science” applies to it. These forms of inquiry become art when they consider how these laws apply in practice.