In this chapter I propose a preliminary response to the transhumanist challenge to natural law by investigating six basic questions: ( 1) Is human nature relevant to morality? (2) Is human nature mutable? (3) How would we know if human nature had changed? ( 4) Could cultural evolution replace biological evolution? (5) How would human nature and human will relate to each other under these new transhuman conditions? (6) Is it possible to construct a dynamic ethic to fit a dynamic nature, and if so, what might that ethic be?

Overall, I argue that it is possible to maintain a natural law ethics approach in the face of transhumanist changes to human nature and that, in fact, doing so remains a very useful approach, albeit one with some difficulties. The norms of natural law are another matter: I think moral norms will need to become either stricter than in the past or different in ways that are difficult to anticipate.

This chapter concentrates on the philosophy and theology of the 13th century Roman Catholic saint, Thomas Aquinas, who developed Aristotle's ideas in a Christian context. Aquinas's claims that action follows being and that human nature is a composite of first nature and second nature are combined with ideas from the philosopher Hans Jonas about the increasing scope of human action and the consequent necessity to update ethics. I propose that there a new form of natural law ethics might be capable of responding to changes in human nature.