Ethical naturalism is the view that ethical claims are either true or false and that their truth or falsity is determined by reference to the external world, either facts about human nature or facts about the physical world beyond humans. Ethical naturalism contrasts with ethical nonnaturalism, which is the view that ethical claims are either true or false but their truth or falsity is not determined by facts about the natural, physical world.

There are two main versions of ethical naturalism. The first can be called virtue-based naturalism. According to standard versions of this view, the question of which acts are right and which are wrong for a person to perform can be answered by appealing to claims about which acts would promote and which would ...