Myron rightly comments “we can’t manage [military] tactics effectively by asking ‘what does natural law teach us here?’” He and I both recoil from the idea that natural law can provide us with much necessary, demonstrable guidance as to regulatory specifics. Nevertheless, today, many Christians turn to natural-law arguments in an effort to demonstrate what the law should be in specific, usually controversial, areas. I suspect that Myron and I share significant doubts about the central role that natural law has assumed in Christian discourse about law. But, as Myron knows, Aquinas would remind us that, regardless of our contemporary practice, the right use of natural law is not necessarily to provide us with general cognitive principles from which particularized regulations can be determined more geometrico.
In addition to necessary logical deductions, natural law may alternatively inspire with a general vision that is given practical determination through the supra-logical art of the craftsman-ruler. Here’s the relevant bit from ST I-II, Q. 95, a 2:
… something may be derived from the natural law in two ways: (1) as a conclusion from premises, and (2) by way of determination of certain generalities. The first way is like that by which, in sciences, demonstrated conclusions are drawn from the principles: while the second mode is likened to that whereby, in the arts, general forms are particularized as to details: thus the craftsman needs to determine the general form of a house to some particular shape.
Aquinas says in essence: all law is derived from natural law – sometimes by syllogism, and sometimes by a process that is like an architect working from the idea of an ecclesial assembly-hall to the Chartres cathedral. Christian natural-law discourse today emphasizes its role in guiding public reasoning far more than its role in inspiring legal craftsmanship, but Aquinas might say that this is a fault of our modern rationalistic practice and not the use of natural law as a source of particular, specific laws.
For those of us seeking to encourage a Christ-centered response to law, the inspirational mode seems like it should be much more important. The Lordship of Jesus may not entail anything about modern law from a deductive standpoint. But it is a matter of historical fact that the life of Jesus and the belief in His Kingdom has successfully inspired a great deal of wonderful practical lawmaking, just as it has inspired a great deal of other art and craft. Cognitively, Jesus may mean very little for the science of aesthetics, but He has inspired vast amounts of our greatest art. Cognitively, Jesus may mean very little for the law, but the vision of His Kingdom, the thought of our Crucified King, has inspired our best legal reforms and structures.
If it is true that as a matter of deduction, Jesus entails little or nothing for law. Then we should conclude that the non-deductive use of natural law is the most significant or only use for Christians. That is, we should be gathering Christian inspiration for lawmaking, not public argumentation for specific policies. Indeed, we might say that the inevitable failure of public reasoning about law in the Christ-less terms of deductive natural-law reasoning is a necessary correlate to Jesus’ Kingship. Moreover, since we believe that Jesus reigns, we should still expect inspiration from Him about our laws, even if we determine that public reason cannot reach the necessary significance of Christ for public life in this age.