Ethical naturalism (also called moral naturalism or naturalistic cognitivistic definism) is the meta-ethical view which claims that:
Ethical sentences express propositions.
Some such propositions are true.
Those propositions are made true by objective features of the world.
These moral features of the world are reducible to some set of non-moral features.
The versions of ethical naturalism which have received the most sustained philosophical interest, for example, Cornell realism, differ from the position that "the way things are is always the way they ought to be", which few ethical naturalists hold. Ethical naturalism does, however, reject the fact-value distinction: it suggests that inquiry into the natural world can increase our moral knowledge in just the same way it increases our scientific knowledge. Indeed, proponents of ethical naturalism have argued that humanity needs to invest in the science of morality, a broad and loosely defined field that uses evidence from biology, primatology, anthropology, psychology, neuroscience, and other areas to classify and describe moral behavior.
Ethical naturalism encompasses any reduction of ethical properties, such as 'goodness', to non-ethical properties; there are many different examples of such reductions, and thus many different varieties of ethical naturalism. Hedonism, for example, is the view that goodness is ultimately just pleasure.
Altruism
Consequentialism
Consequentialist libertarianism
Cornell realism
Ethical egoism/ Objectivism
Evolutionary ethics
Hedonism
Humanistic ethics
Natural-rights libertarianism
Utilitarianism
Virtue ethics
Ethical naturalism has been criticized most prominently by ethical non-naturalist G. E. Moore, who formulated the open-question argument. Garner and Rosen say that a common definition of "natural property" is one "which can be discovered by sense observation or experience, experiment, or through any of the available means of science.