 Aquinas says that the fundamental principle of the natural law is that good is to be done and evil avoided (ST IaIIae 94, 2). This is, one might say, a principle of intelligibility of action (cf. Grisez 1965): only action that can be understood as conforming with this principle, as carried out under the idea that good is to be sought and bad avoided, can be understood as an intelligible action. But no one can in acting simply pursue good — one has to pursue some particular good. And Aquinas holds that we know immediately, by inclination, that there are a variety of things that count as good and thus to be pursued — life, procreation, knowledge, society, and reasonable conduct (ST IaIIae 94, 2; 94, 3) are all mentioned by Aquinas (though it is not clear whether the mentioned items are supposed to constitute an exhaustive list).