We therefore reject every attempt to impose on us any moral dogma whatsoever as an eternal, ultimate and for ever immutable ethical law on the pretext that the moral world, too, has its permanent principles which stand above history and the differences between nations. We maintain on the contrary that all moral theories have been hitherto the product, in the last analysis, of the economic conditions of society obtaining at the time. And as society has hitherto moved in class antagonisms, morality has always been class morality; it has either justified the domination and the interests of the ruling class, or ever since the oppressed class became powerful enough, it has represented its indignation against this domination and the future interests of the oppressed. That in this process there has on the whole been progress in morality, as in all other branches of human knowledge, no one will doubt. But we have not yet passed beyond class morality. A really human morality which stands above class antagonisms and above any recollection of them becomes possible only at a stage of society which has not only overcome class antagonisms but has even forgotten them in practical life.
— Friedrich Engels, Anti-Dühring