Moral relativism is the theory that moral standards vary from society to society, and from time to time in history. Under this theory, ethical principles are not universal and are instead social products. This theory argues that there is no objective moral order or absolute truth. Indeed, variability in what is seen as moral is seen throughout history: with the genocide of the Jews by the Nazi Party, the enslavement of the African people by both European and American powers, the persecution (including torture and murder) of Christians during Roman times and in Communist states, as well as the torture, imprisonment, and murder of scientists during the Eighteenth century by the Catholic Church, all justified by the perpetrators in moral terms. For example, Hitler justified his racial policies by saying:
- The greatest achievements in intellectual life can never be produced by those of alien race but only by those who are inspired by the Aryan or German spirit. In view of the narrowness of the space within which German intellectual work and German intellectual workers have to live they had a natural moral claim to precedence and preference. 
Similarly, the case for slavery was often made in moral terms, with Thomas Dew arguing in 1832 that:
- With regard to the assertion, that slavery is against the spirit of Christianity, we are ready to admit the general assertion, but deny most positively that there is any thing in the Old or New Testament, which would go to show that slavery, when once introduced, ought at all events to be abrogated, or that the master commits any offence in holding slaves. The children of Israel themselves were slave holders, and were not condemned for it.…When we turn to the New Testament, we find not one single passage at all calculated to disturb the conscience of an honest slave holder. 
In recent times, according to the Discovery Institute:
- Moral relativism was uncritically adopted by much of the social sciences, and it still under girds much of modern economics, political science, psychology and sociology. 
Examples of Moral Relativism
The use of Waterboarding as an interrogation method is a case where a tactic that led to the war-crime prosecution of a Japanese officer for using it on Americans in WWII  was sanctioned by the administration of President George W. Bush for use on for high-value terror suspects. The moral issues in this case are defining when an interrogation technique crosses the line from appropriate to inhumane (torture), and to what extent the risks of a clear and present danger to a nation justify the use of questionably inhumane methods to save innocent lives.