Legal philosophers tend, as we noted in Chapter 1, to treat John Finnis's book Natural Law and Natural Rights as a freestanding account of the nature and rightful purposes of law. To properly understand Finnis's work – both in Natural Law and Natural Rights and elsewhere – it is, however, crucial to pay attention to his acknowledgment in the preface that there may not be “much that is original” in the book's argument and that the “ethical theory” and “theoretical arguments” advanced in its central sections are “squarely based” on his understanding of the work of Germain Grisez, a theologian and moral philosopher described by Ralph McInerny as “one of the most important Catholic moralists of our time” and the preeminent and original new natural law theorist. Natural Law and Natural Rights has certainly played an important part in the development of new natural law but it is not the conclusive or definitive statement of the theory, which is as much concerned with theology and ethics as it is with law.

Apart from Grisez and Finnis, other important actors in developing or supporting new natural law include theologians Joseph Boyle and William E. May, as well as Russell Shaw – who converts theological texts into language accessible to non-theologians.