In the preface to the second edition of J. Budziszewski’s What We Can’t Not Know: A Guide he gives a brief account of the history of natural law theory (a meta- and normative ethical theory very much at home in, but not limited to, Aristotelian-Thomistic philosophy). I liked it, so I’m quoting it at length:

Speaking in the broadest possible terms, the natural law tradition has passed through three historical phases and is now entering the fourth.

Phase one belonged to the philosophers. Ancient thinkers like Aristotle discovered that beings have natures, and tried to develop intellectual tools for thinking about them. Other thinkers, especially the Stoics — although this idea is present in embryo in Aristotle too — suggested that the principles of these natures could be expressed in terms of laws, real laws, which were somehow the work of the divine mind.

Phase two belonged to the theologians. Jewish thinkers worked out the implications of the ancient tradition that before God gave the Torah to the “sons” or descendants of Abraham, He had already given commandments to the sons of Noah, which means to the whole human race. Islamic thinkers of the now much less influential Mutazilite school maintained that good and evil are embedded “in things”, in the structure of creation. Christian thinkers explicitly appropriated the whole philosophical tradition. As Joseph Cardinal Ratzinger suggested before his accession tot he papacy, in the early days of Christianity, “in an environment teeming with gods”, when believers were asked to which god their God corresponded, “the answer ran: to none of them. To none of the gods to whom you pray but solely and alone to him to whom you do not pray, to that highest being of whom your philosophers speak.” He rightly remarks, “The choice thus made meant opting for the logos as against any kind of myth”, he pointedly adds, “By deciding exclusively in favor of the God of the philosophers and logically declaring this God to be the God who speaks to man and to whom one can pray, the Christian faith gave a completely new significance to this God of the philosophers… [T]his God who has been understood as pure Being or pure thought, circling round forever closed in upon itself reaching over to man and his little world… now appeared to the eye of faith as the God of men, who is not only thoughts of all thoughts, the eternal mathematics of the universe, but also agape, the power of creative love.” In the natural law, the power, love, and wisdom of this God were united, and in the grace of Christ the capacity to follow it was restored. Here I must repeat another point from the first edition: although the thinkers of these faith communities were mindful of their traditions, they were not hermetically sealed from each other. It was no accident that the period during which the thinkers of my faith achieved their greatest insights into natural law coincided with the period during which they were intensely and simultaneously engaged with the pagan thought of Aristotle, the Jewish thought of Maimonides, and the Mulsim thought of Averroës.

Phase three was dominated by the thinkers of the Enlightenment. For various reasons — in some cases religious skepticism, in others fear of religious wars — they tried to sever the connections between religion and philosophy, between faith and reason. Their aim was to make natural law theory theologically neutral — a body of axioms and theorems that any intelligent, informed mind would consider obvious once they were properly presented, in fact equally obvious no matter what religion of wisdom tradition the mind followed, or whether it followed any at all. It wasn’t that the Enlightenment thinkers didn’t believe in God. Although some were atheists, others were Christian, of a sort. The problem was somewhat different, and it was twofold.

In the first place, they thought that one could know all the important things about man even while knowing very few of the important things about God. It was enough to work out His existence as a theorem; there was no further need to know His name, the history of His self-disclosure, His mighty deeds in history. In one way this was a regression to the Unknown God of the Athenians, to the “pure Being or pure thought, circling round for ever closed in upon itself without reaching over to man and his little world”. Yet like all apparent regressions, in another way it was not that at all; whenever we try to return to an earlier stage and reject what we have learned since then, we lose what we had then too. The problem with the Athenians was simple ignorance; they had never heard about agape. The problem with the thinkers of the Enlightenment was rejection; they had header about agape but decided that it wasn’t important. This was a kind of intellectual blindness, and it was progressive. Having lost their grip on agape, they came to lose their grasp of the logos too. Consequently, they felt a greater and greater need to make natural law theory to be not only theologically neutral but even ontologically neutral, independent of anything else that might be important. And this was impossible. In the second place, they thought that the ability of the mind to grasp the truth about man was independent of moral virtue. To put it another way, ethics was like mathematics. A scoundrel ought to grasp the virtue of purity just as easily as he grasped the Pythagorean theorem — and if he couldn’t, then perhaps that showed it simply wasn’t a virtue. Needless to say, this had a certain flattening effect on moral philosophy.

The reason we are entering a fourth phase is that the Enlightenment project collapsed. Modern man lost confidence in the possibility of an ethics that was both universal and yet somehow neutral. Some, relativists, retained the idea of ethics but abandoned the idea of universality; they thought each group has its own right and wrong. This reduces statecraft to sheer power, because someone’s right and wrong has to win and there is no way to arbitrate among them. Other, liberals, retained the idea of neutrality but abandoned the idea of ethics. They came to insist that the laws of the state must be justified in a way that is independent not only of theology and ontology, but of “one’s conception of the good”. Because this is impossible, what happens in practice is that their own views of the good prevail without challenge, just by pretending that they aren’t really views of the good.

In this nascent fourth phase, natural law thinkers are beginning to follow a different path. While retaining the idea of a universal ethics, they have abandoned the Enlightenment fallacy of neutrality. Is there a common ground? Yes, because there is a single human nature. But is the common ground a neutral ground? No, because not all views of God, not all views of the structure of reality, not all views of human nature itself are equally adequate, and some make it harder to see the common ground. The new breed of natural law thinkers also reject the fallacy that natural law is like mathematics. To see it well, one must have pure eyes, and this requires moral virtue. Here we enter, not a vicious circle, but what may be called a virtuous circle. The more adequately one has been shaped and formed by traditions and disciplines that conform to the natural law, the more clearly one can discern the underlying moral realities on which these disciplines are based.

Now let me draw some of the consequences. Future natural law philosophers will be free of the delusion that once can reason about natural law independently of how well one has been brought up, in what one places faith, or to what intellectual tradition one is loyal. Natural law theory is itself the product of a tradition, and it thrives better in the soil of some faiths than others. It may seem that this implies that the whole aspiration of natural law is a failure: that there is no universal ethics, that just because our roots suck up nourishment from different traditions, we have nothing to say to each other. On the contrary, what it really implies is that there must be a new way of speaking together. The Enlightenment thought we could speak with each other only by setting aside our traditions and regarding them as irrelevant — it was an antitraditional tradition, which could never look at itself in the mirror for fear of discovering the incoherency at its foundation. The truth is that we must speak with each other from within our traditions, because only these give us something to say to each other. As the first edition suggested, even the appeal to the generic presupposes the particular; for insight into what we hold common, we must fall back on what we do not hold in common. Consequently, rather than being divorced from theology, natural law theory must be reintegrated with it — not despite the desire to find common ground, but even because of it.

Clearly there are many thoughts to be fleshed out in the remainder of the book. I look forward to it.