While I was away on vacation, Rod Dreher and Alan Jacobs got into an interesting conversation about why and how arguments from natural law fail. The thrust of the conversation was about what to do about the fact that such arguments fail, and how that should impact the way people who do believe in such arguments should argue, in the public square. But, at the risk of merely proving their point, I’d like to actually join the argument that exists ontologically prior to their argument. Because I’m one of those people who don’t really “get” natural law arguments. And I consider myself to be sufficiently open-minded that I’d like to believe I could reject – or affirm – such arguments rationally.

Why do I say I don’t “get” natural law arguments? Because I don’t understand what’s “natural” about them.

If I understand the way natural law is supposed to work, it’s supposed to be an instance of deriving social “oughts” from a natural “is.” Human beings have to some degree immutable natures, natures we can comprehend with reason, and these natures determine, to a considerable degree, what social arrangements will “work” and what arrangements won’t – in the sense of contributing to human flourishing.

I don’t have any objection to the foregoing, which seems like a straightforward and pragmatic reading of Aristotle (though not the only possible reading by any means). If I understand where Christian versions of natural law take this, they ascribe teleological meaning to our natures, because these natures were intended to be as they are (created, as they were in this understanding, by God). Thus, it’s not merely a matter of our natures constraining what we can do without ultimately making us unhappy (in the deepest sense of happiness), but that we should be happy with the fact of that natural constraint. I’m not sure how much of a difference that pragmatically makes, but even positing that it does make a difference, I can certainly follow the argument, and I won’t reject it out of hand or argue with it here.

But then there’s another step to the argument: what is the epistemology that is necessarily prior to the determination of what this natural law is? In other words, how do we know what our essential natures are?

These days, the rubber usually meets the road on questions of human sexuality. For example: is homosexual behavior natural or contrary to nature properly understood? Someone taking the former position would probably argue, on both scientific grounds and on the grounds of personal or reported experience, that sexual orientation is innate, and therefore natural. Someone taking the opposite position would then say that this is not what “natural” means in this context – after all, a predisposition to alcoholism may also be innate, as may sociopathic tendencies. Just because they are innate doesn’t mean they contribute to human flourishing – that they are in harmony with our deepest natures, with what we, as human beings, could or should be.

At which point the person taking the first view would probably argue: well, how do you know whether a given predisposition is in that harmony? It sounds like you have some other theory for deciding what is right and what is wrong, and that you are deciding what is natural on the basis of that list, not the other way around. Well, I can play that game, and my theory is Millsian preference utilitarianism. And on that basis, there’s nothing a priori wrong with any particular sexual act between consenting adults, so a homosexual orientation can’t be “disordered” – it’s just a morally neutral fact.

The natural-law enthusiast would respond: you’ve got it all backwards. I’m not starting with a list of “thou shalt nots.” I have a detailed theory about the shape of human nature, derived from very basic observations and self-evident assumptions. Indeed, there’s a whole philosophical tradition behind my theory, which it would behoove you to master before dismissing it. And homosexual behavior simply doesn’t fit the theory. It isn’t in harmony with the human telos – not merely in the sense of what this or that body part is “for,” but in the sense of what we as humans in our entirety are for, what our natures made us for.

And at this point, if I were in the debate, I would say: okay, how do we know that your theory is true? What is its evidentiary basis? And I don’t know what the answer would be from the natural law side – indeed, I’ve never heard a proper answer.

From what I understand from the kinds of arguments that natural law types make in public, the answer to this question is resort to the history of scholastic philosophy. But I can’t see why that should be the right answer. Aristotle’s reasoning is as good now as it was when he tutored Alexander, but his science emphatically was not as good then as ours is now. And Aristotle thought he was doing science – “metaphysics” was just the stuff that came after physics, another book on the same shelf, not an entirely distinct category of thought.

The people who, today, seem to me to be making “natural law” type arguments of the sort Aristotle himself would recognize are the evolutionary psychology folks – the people who are trying (we can debate with what success) to develop a genuinely scientific genealogy of morals, to know our natures by understanding, scientifically, how they got that way. But this isn’t at all what people who call themselves supporters of a “natural law” approach to law and ethics do.

It seems to me that this is the reason that natural law arguments fail in practice. It’s not that we can’t accept that we have natures, or that those natures might be constraining in one fashion or another – outside of certain politically touchy topics, we entertain the idea that our natures constrain us, and how we can pursue (and achieve) happiness, all the time. It’s that the advocates of a natural law approach cannot explain adequately how they know what they claim to know about our natures, and expose that purported knowledge to scientific criticism of the kind that we would recognize if the question were, say, “do dogs feel pain?” And the suspicion grows, over time, that this question isn’t opened not because it cannot be opened but because it must not be opened, because it is really the conclusions that are “known” absolutely, and not the premises.

None of which obliges people who do adhere to, say, the traditional Christian view on homosexuality to change their minds. Even if they come to conclude that what Thomas Aquinas’s “knew” isn’t knowledge in the same way that, say, our modern understanding of fluid dynamics  is, that doesn’t mean they can’t behave “as if” it is the same kind of knowledge. It’s just going to be hard to convince people who don’t already believe that – because that act of behaving “as if” is, effectively, an instance of positive law rather than natural law.

Allow me to make an analogy to my own religious tradition. You may be aware that the kashrut laws are considerably ramified in rabbinic literature from the spare rules outlined in the Pentateuch (which consist, basically, of a list of prohibited animals and the thrice-repeated rule not to “seethe a kid in its mother’s milk” which probably originally referred to a Canaanite fertility ritual). One rabbinic precept with regard to the kashrut of utensils is that the mode of cleansing utensils that have been contaminated by contact with unkosher food (or unkosher mixtures of food) varies based on nature of the utensil and the nature of the contamination. Porous utensils – e.g., wood – cannot be cleansed by any means. Glass utensils, which are deemed non-porous, can be cleansed by simple washing. Metal utensils, which are an intermediate case, are subject to cleansing by greater heat than was applied to create the contamination – contact with a cold contaminant can be cleansed by simple cleaning, contact with a hot contaminant can be cleansed by immersion in boiling water, and of the contaminant was hotter than boiling the utensil can be cleansed by direct exposure to fire.

Now, all of these distinctions were, from the perspective of the rabbis making them, scientific. That is to say: they were trying to apply revealed law scientifically, because they wanted to apply that law correctly. The revealed law said to break a non-kosher utensil; science would tell what kind of contact with non-kosher food makes a utensil non-kosher.

But that doesn’t mean they got the science right. The rabbinic notion that hot food “bonded” with a metal utensil has no particular basis in scientific fact. The kosher rules do not perfectly track, for example, rules for avoiding contamination by allergens.

Sometimes the kosher laws are “too stringent” in scientific terms; other times they are too lax. Honey is kosher – because the rabbis thought that it was collected by bees, and not processed by them internally. But of course, it is nectar that bees collect, which is processed by them internally to become honey – which “should” render it non-kosher. Meat that develops maggots, similarly, may not pass muster with Federal regulators, but it’s kosher – because the rabbis thought the maggots developed by spontaneous generation, and were therefore of the same substance as the meat. If the meat is kosher, the maggots are kosher. But maggots do not develop from spontaneous generation – they hatch from eggs laid by flies.

Have the laws of kashrut been modified to account for new scientific knowledge? The Orthodox Jewish answer is: no. The rulings of the tannaim and amoraim remain valid. Honey is still kosher. You cannot cleanse a metal pot merely by putting it in the dishwasher. But this approach effectively divorces those rulings from nature, and turns them into purely positive law. This or that is no longer kosher because of some understanding of actual reality – kashrut is simply a matter of applying rules.

From my perspective, the natural law approach to human sexuality looks pretty similar. There is a scholastic tradition, rooted, originally, in direct investigation of the natural world, that attempts to discern essential truths about human nature. Certain conclusions may or may not derive readily from the axioms of that tradition, but even granting for the sake of argument that they do, those axioms ought, if the theory is actually a theory of nature, be subject to scientific investigation, and held tentatively as all scientific theories are. If they are not, then we aren’t really talking about a theory of nature. In which case we should be calling it something other than natural law.

All of that having been said, I should add that many of the most interesting questions are not readily answerable – even tentatively – from a scientific perspective. But that doesn’t really matter. There’s a huge difference between saying, “I know that human nature works this way,” and “it makes sense to me that human nature works this way – it resonates with me emotionally – and there’s both a considerable philosophical tradition and a voting majority that agrees with me.” Natural law arguments are precisely intended to move from the latter to the former formulation – to get us away from “emotivism” and preference-utilitarianism and so forth, without falling into the alternative of Hegelian historical relativism (an alternative that, I should note, Alasdair MacIntyre accepted as necessary). I’d like to understand better why reason dictates that I assent to that move.