Ethical Naturalism

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 undermine that person's living a life that is good for human beings to live. This is a natural approach to ethics as it purports to explain when an act is right or wrong in a fully natural way, without referring to any nonnatural source of moral value. This virtue-based naturalism is based on the view that there is a distinctive way of living that human beings are best suited to pursuing and that if they were to pursue this, they would flourish. The primary objection to such virtue-based naturalism is that there is no such distinctively human life, and so it is not possible to determine if an act is right or wrong in terms of whether it is in accord with such a life or not. It is also often charged that this approach to naturalism faces an epistemological difficulty: that even if there was a distinctively human life that could ground claims about the rightness or wrongness of actions in this way, we would not know what form it would take. However, even if this last objection is correct, that we cannot have this access to the rightness or wrongness of actions, it does not show that this naturalistic account of what makes an action right or wrong is incorrect. It just shows that we cannot know when an action is right or wrong.

The second version of ethical naturalism, which can be termed metaethical naturalism, is the view that moral philosophy is not fundamentally distinct from the natural sciences. This is the version of ethical naturalism that is most often understood to be at issue in discussions of the “naturalistic” approach to ethics. On this approach to naturalism, moral value—that is, roughly, the rightness or wrongness of an action—should be understood as being defined in terms of (or constituted by, or supervening on) natural facts and properties. For example, John Stuart Mill's utilitarian approach to ethics was a naturalistic approach of this sort. For Mill, an action was morally right insofar as it tended to promote happiness and wrong insofar as it failed to do so. Since for Mill happiness was defined in terms of pleasure and the absence of pain, which are natural properties, the rightness or wrongness of an action can be explained in terms of natural properties.

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