 Return to Aquinas’s paradigmatic natural law position. His account of our knowledge of the fundamental goods has been understood in different ways (Murphy 2001, ch. 1). Some have understood Aquinas as affirming a theory of our knowledge of the fundamental precepts of the natural law that we can label ‘derivationism.’  The idea here is that we can derive from a metaphysical study of human nature and its potentialities and actualizations the conclusion that certain things are good for human beings, and thus that the primary precepts of the natural law bid us to pursue these things (cf. Lisska 1996). One can imagine a Hobbesian version of this view as well. One might say that by a careful study of the human being’s desire-forming mechanisms, one can see that there are certain things that would be necessarily desired by biologically sound human beings, and thus that the human good includes these items. (Hobbes in fact produces such arguments at [EL], I, 7.)  While a natural law theorist might downplay the importance of derivationist knowledge of the natural law, it is hard to see how a consistent natural law theorist could entirely reject the possibility of such knowledge, given the view that we can provide a substantial account of how the human good is grounded in nature: for to show that the human good is grounded in nature is to show that human nature explains why certain things are goods, and it is hard to see how one could affirm that claim while entirely rejecting the possibility of derivationist knowledge of the human good (see Murphy 2001, pp. 16–17). Some have thought, echoing criticisms of natural law theory by those entirely hostile to it, that derivationist theories of practical knowledge fall prey to ‘Hume’s Law,’ that it is impossible to derive an ‘ought’ from an ‘is,’ that is, any normative truth from any set of nonnormative truths. The most that this can show, though, is that the natural law theorist needs an account of those bridge truths that enable us to move between claims about human nature and claims about human goods.