Sexual Ethics, Human Nature, and the “New” and “Old” Natural Law Theories

The major difference between “new” and “old” natural law approaches to sexual ethics is that for new natural law theorists the moral evaluation of sex acts is always determined with reference to that basic form of human flourishing which is called marriage; old natural law theorists determine the morality of sex acts also with reference to the natural purpose of the sexual faculties. Ultimately, the old approach relies implicitly on prior value judgments to distinguish biological facts that are axiologically or morally relevant from those that are not. It also appeals to values to ground the wrongness of immoral sex acts. In its pure form, the old natural law approach to sexual ethics lends itself to a misunderstanding of the unitive aspect of marriage. More broadly, an accurate understanding of new natural law does not run afoul of the correct interpretation of “nature” in natural law.