Are there moral facts? Is there a moral reality independent from us? Naturalist moral realists think exactly that, construing ethics as a fact-stating discipline and drawing a strict parallel between ethics and science. In short, they argue that moral statements are on a par with empirical claims and made true by moral reality – where moral facts are nothing over and above natural facts. If this realist venture proved successful, normative research – both within philosophy and political science – would be placed on a solid, scientifically respectable footing. With good conscience, we could continue to enquire into those questions which are arguably the most interesting – such as queries about just wars, the supremacy of democratic over dictatorial systems or the justification of laws permitting or prohibiting stem-cell research and the shooting down of planes in terrorist attacks. But, are ethics and science really on a par? Christine Tiefensee sets off to put moral realism under close scrutiny, analysing its tenability according to its ontological, epistemological, semantic and psychological theses. Will moral realists prove to be right?