To examine the prospects for natural law ethics, we need first a working definition of it. But as the previous chapters suggest, any such definition is controversial. Thomas Aquinas defines law as ‘an ordinance of reason directed towards the common good from him who has care of the community and promulgated’. It follows that for a law to be natural, it must be not only grounded in human nature – something Aquinas affirms elsewhere – but also promulgated: the only available promulgator being God. Rosalind Hursthouse, by contrast, takes natural law ethics to be metaphysically less demanding. For her, its theistic underpinning is not salient, and appears even moot. What is salient is the provision of a naturistically grounded criterion of right or good action. Natural law ethics is thus distinct from ethical naturalism in general, which ‘provides a criterion for a particular trait’s being a virtue, not a criterion of right or good action, except indirectly’.