I'm not trying to be a contrarian here (or at least not trying to only be a contrarian), but I'm not sure that the legal positivists are discounting the moral content of law, so much as they are disagreeing that law necessarily always has moral content.
When I read Hart or Jules Coleman or the other soft-positivists, I'm understanding them to say that morality can be made a part of law, but that morality is not necessary for something to be conceptualized as "law."
For example, the soft-positivists would say that the posited "laws" in the antebellum United States allowing for ownership of other human beings were "bad laws" and "evil laws," but were definitely "laws" because (in an oversimplification) those posited laws did what laws are generally understood to do. Or, to put it differently, they had all the characteristics that any other things understood as "laws" have, with the only exception being that they were "morally evil" as opposed to "morally good" or even "morally neutral."
Natural lawyers would have to argue that all of those posited slavery laws allowing for ownership of other human beings were "not really laws.
And that's fine, except it doesn't really contain any meaningful explanatory force.
As an (admittedly crude and simplistic) example, you could tell me that even though you hurt your hand and you can't close your first, you are going to punch me in the face.
I could give you a 500 page thesis on why it's not really going to be a punch, because the concept of a punch requires a closed fist and a particular positioning of the hand, etc...therefore, what you are going to do isn't really punching me in the face.
How will any of that explain why, as far as the practical and conceptual implications are concerned, when you uppercut me to the jaw with the flat inside part of your open palm, it has the EXACT same form, function, and outcome as if you had used a closed palm such that it fits squarely within the clear concept of a "punch?"
Same with natural law theory.
It doesn't really DO anything useful when it comes to explaining Law.
That's not to say that it's not incredibly useful when it comes to making a normative justification or explanation of what laws ought to be.
But saying that "Natural Law theory explains what laws OUGHT to be" is very different than saying that "Natural Law theory explains what is or is not law."
Put differently, positive lawyers and natural lawyers really are doing two different things, and should stay in their own lanes.
Positive lawyers have a robust theory for describing law and what law is. Sometimes those descriptions include morality and sometimes they don't, depending on whether that particular law has a moral dimension that is definitionally part of that law. (I know Raz disagrees with this, and he's brilliant, but I think he's probably wrong).
Natural Lawyers have a robust theory for prescribing law and what law ought to be.
Positive legal theory really has nothing to say about what law ought to be. But, similarly, natural law theory really has nothing to say about what law is.
In any event, thanks for the article. You got the synapses firing in parts of my brain that I haven't used in a LONG time. It feels good.
Hope we can continue the discussion, I'm enjoying this immensely :)
Thank you for the engaging reply, and sorry for not responding earlier!
First, let me say that this is by no means a comprehensive look at natural law theory vs. legal positivism, and you bring up excellent points. While I generally agree with you, I'd argue that even natural law theory describes what law is. For example, for Aquinas, a law is an "an ordinance of reason for the common good, made by him who has care of the community, and promulgated." I'd argue that anyone who is attempting to explain what law ought to be necessarily would have to describe what law is in order to make their prescription. You can't evaluate whether something has particular qualities unless you describe what those qualities are in the first place.
Recall that Plato and Socrates both posited that even unjust law still has the form of law. This is a common mischaracterisation of the arguments put forth regarding what is truly law. An arbitrary edict by a ruler would be unjust in classical natural law theory, but nowhere will you find these theorists advocating for unqualified disobedience to those laws. They recognized that those laws still had the form and force of law, even if they were unjust. Martin Luther King, Jr., paraphrasing Aquinas, said as much when he was imprisoned for his civil disobedience.
Additionally, legal positivism does generally avoid discussion of moral content in law. That's not to say that legal positivists don't give the topic thought at all. As you pointed out, they may argue one way or another, but their primary (and many times sole) focus is on identifying laws and their operation. Bentham was notoriously averse to ascribing any moral content to law, and Austin argued that morality was totally inconsequential to the law. The legal realism and law and economics approaches likewise discount any moral content as not being relevant to the discussion of what law is.
They often fail at that, as they have to answer why any law, no matter how well-formulated and efficient, should exist at all. Any evaluation of a law has to take this question into account, and the most that can be said from the legal positivist view is "because the sovereign says it is so."
I don't disagree that the two approaches have their respective strengths, but I'd argue that they can compliment each other and there is some overlap. However, the reason why natural law theory is my favorite is because any discussion of law should start from asking if a law is necessary at all to regulate conduct. Arguably this goes back to the Greeks as well (reconstituted and included by Finnis as one of his seven universal goods; knowledge), as the Stoics felt that pursuing knowledge was a virtue, and this pursuit almost invariably begins with the question why. It's part of the human experience to question. :D
I'm looking forward to your response! Out of curiosity, what is your background? You seem well-versed in jurisprudence, so I'm guessing you've at least studied law, if you're not a lawyer.