A reader weighs in with a comment on Natural Law which is more clearly written than what I could say. Allow me to reprint his words here without further comment from me:
Here’s hoping our host won’t mind if a longtime lurker waxes philosophical a bit in defence of the natural law. While it’s true that the natural law arises somewhat spontaneously in men through the moral intuitions, it seems to me that these are only failsafes should we happen to discard our intellects. Mr Wright’s account of the natural law might benefit from the introduction of some metaphysical components that to clarify matters to the honest sceptics in his audience. If one allows for an Aristotelico-Thomistic view, the Natural Law should be rationally defensible (and, I believe, has been held to be so by philosophers from Aristotle to Aquinas) even to one who initially doubts its existence or has corrupt moral intuitions.
The traditional natural law theory is grounded in the idea of teleology or Final causality, which is the idea that things are, by nature, directed towards specific ends, and the idea of Formal causality, that things have a particular substantial form in virtue of which they are what they are. Together, they are the two forgotten members of the Four Causes which have been banished by the modern materialist or mechanistic paradigm to frankly disastrous effect. Of course, the two causes that remain, Efficient and Material causes, are unintelligible without these former two, a consequence which the materialists seem to be for some reason blissfully unaware of.
The idea of Final Causality is obvious in the existence of potentialities and powers, for potentialities are always, insofar as they are potentialities, potentialities *for* something. There is in every potency a directedness toward a particular end or range of ends, so to deny final causality is just to deny the existence of potencies and powers, which, if any sceptic should be insane enough to do so, would be to deny their own intellect, which just is a set of capacities for grasping truth. As for Formal Causality, to have a Formal cause, or Form, is to have a particular sort of distinctive essence, or what it is to be a thing, a quiddity that separates a type of thing from all that is not of that type. That there should be different and distinct things in the world at all is only, it seems to me, intelligible if one accepts the idea of essences that inhere in various things. That these sorts of causes are furthermore deeply interrelated with Efficient and Material causes is easily demonstrable. Efficient causes are only intelligible if one accepts Final causes, for how is there to be the actualization of potency (which is what Efficient causes consist in) if there is no directedness of potency toward an end, and thus, no potency at all? Material causes seem to be reliant on Formal causes in much the same way, for how is it that a thing could be composed of a particular material and not others if there is no such thing as what it is to be a particular material?
The implications of the existence of Formal and Final causality for our idea of natural goodness, from which natural law is derived, are profound. If a thing’s nature consists in having a particular final cause or set of final causes, then the degree to which it attains those ends is the degree to which it achieves its own nature, and thus becomes an objectively *better* example of what it is. For such things, there is such a thing as what it *ought* to be, in order to be what it is; the final ends of such a thing prescribe the good *of* that thing in a real, objective and discernible way. It happens, of course, that humanity is just that sort of thing. The nature of Man is to be a Rational Animal- the rational faculty being a functional capacity directed at grasping the truth through the employment of the intellect, and animalness being a hierarchy of thousands of bodily capacities each in directed towards their own respective functional ends which play a role in the whole. Insofar as each of those capacities is performing its role in the functional hierarchy, goodness, or flourishing, obtains in a man, and insofar as those capacities or misdirected or destroyed or otherwise distorted from their proper harmony, harm and defect occurs in him.
Moral goodness in particular is that subset of natural goodness that has to do with whether or not one’s will conforms to one’s natural good. If a man be of good will, he will not purposely seek evil or defect, but will rather seek the perfection of his nature as he grasps it by reason, which will entail, among other things, that he seeks the good of his fellow-man (as he is a social creature), tries to be a good citizen ( as he is a political creature), tries to be chaste or a loyal spouse to his wife (in accordance with the unitive and reproductive ends of the sexual nature) and especially to be a holy servant of God (as he is a created being, and thus created for God). A man of wicked or evil will, by contrast, will seek what is perverse or intrinsically contrary to the ends at which his nature is intrinsically directed. He cannot, of course, erase that directedness, but he can orient himself toward total failure in achieving the good.
Moral obligations, the “Law” part of “Natural Law,” follow at last from the realization that the finality inherent in human nature is there in virtue of the will of an intelligent power, that wills our good for us, and whose will for our will constitutes what our will ought to be; nature testifies, in short, to normative imperatives from God, or natural obligations, that determine for us what we ought and ought not do, and makes goodness a duty, and badness wrongness.