When it comes to ordinary crime, for example mugging and burglary, natural law is obvious:
What is crime?
Crime is bad actions that are apt to be met by physical violence, socially approved physical violence.
What is law?
Law is social approval for violence against certain kinds of bad actions.
If you see a conflict between someone who is mugged, and someone who is mugging, you will naturally support the victim and oppose the aggressor, because the aggressor might aggress against you, so, natural law. It is natural for everyone to support violence against certain kinds of acts, so those acts are naturally crimes, and violence against those acts is naturally law.
If the state goes with the grain, making illegal those things that are naturally crimes, and not making illegal those things that are not naturally crimes, order is easy. If it runs against the grain, the state creates disorder.
However, when Catholics talk about natural law, they are generally not talking about this obvious, uncontroversial, and straightforward natural law, natural law relating to uncomplicated crime, but about sex.
And the rules on sex are a lot more socially contingent that the rules on violence. It all depends. Which is not to say that progressives can make up any rules they feel like and expect them to work, so in that sense, there is natural law on sex, but in that what is natural depends a lot on socially constructed circumstances, there is no natural law on sex.
What is natural is feral behavior. Natural law is those restraints that are natural to impose on feral behavior – we are disinclined to tolerate predation on people like ourselves, or parasitism on people like ourselves.
Feral female behavior is hypergamy. Women unrestrained by male authority will sleep with the top few percent of men, which means that those men at the top are disinclined to be fathers to their children, and the rest of the males have no children. Such a society is dysfunctional because the males are disinclined to work, to fight in defense of their society or its women or children, or to transmit their culture to the children. Idle hands lead to widespread criminal behavior among the males.
Such a society is indeed natural, but lacks laws on sex.
Now let us imagine a society with strong families, and little or no welfare for bastards. Such a society is not a necessary product of natural law. Rather it requires the patriarchs to agree together to support each other’s familial authority. While the lack of welfare is natural, (welfare needs to be socially constructed) strong families are not natural. Strong families need to be socially constructed.
But, given strong families, the patriarchs will wind up carrying a large party of the externalities of feral female sexual conduct. So, naturally, they simply will not allow feral female sexual conduct. Thus, in such a society, severe restraints on female sexual conduct and a strong guiding hand on female sexual choice (only approved suitors allowed, dads, not cads) are indeed natural – natural law, given the not all natural social construction of patriarchal familial authority.
The Roman Catholic “natural law” on sex is only natural for a society with strong families, where contraception is ugly and unpleasant, where abortion is dangerous, and, most importantly, where maternity is a matter of fact, but paternity is a matter of opinion.
The Roman Catholic Church, however, was at the forefront of undermining strong families, sawing off the branch on which they sat. The original Roman marriage, on which Christian marriage is based, was contract between the bride, the groom, and the patriarchs of the families, wherein if the bride or the groom broke his vows, he was not only breaking his oath to his spouse, but to his father. The Christian Church, and in particular and especially the Roman Catholic church, progressively erased the role of the family in the marriage, making it a contract between the bride, the groom, and God, with the parents of the bride and groom merely passive onlookers. In this sense, Christianity has been leftism for a very long time. That the heretical spawn of Christianity disowned first Jesus, then God, was a consequence of that leftism.
Successful past societies took extraordinarily drastic measures to ensure certainty of paternity. In this sense, certainty of paternity is socially constructed, and you need paternal certainty for strong families. Today, however, paternity is as much a matter of fact as maternity, a change that should lead to social changes more drastic than those of the contraceptive pill, but as yet, those changes are suspended, held at bay by a government hostile to fatherhood, that wants women married to the state, and married to their job, rather than married to husbands. Routine paternity testing is socially and legally discouraged, and the law ignores actual paternity for supposed social paternity, treating paternity a matter of opinion, which legal policy is running headfirst into reality. Males care very much about actual paternity, and if it differs from social paternity, are apt to get upset, often homicidally so. One suppose that since paternal certainty was not available in the ancestral environment, males would only care about social paternity, but evidently humans have understood the connection between sex and reproduction for long enough to select for males who care about actual paternity – the latest technologies are a very large change in degree, but not a change in kind.
We can today have the kind of society that past people’s had without the need for as much tight control on females, because we can know who the father is without keeping wives entirely locked up and putting them in chadors. So the natural outcome of this improved technology is return to patriarchy, where fathers are entitled to be fathers, and women are forbidden to have children by more than one father – because today it is easier to enforce a prohibition on women having children by more than one father.
Sexual behavior is apt to be subject to very strong selection effects, resulting in remarkably rapid evolution. Condoms are the oldest form of contraception, and evidently in the short time they have existed, many males have evolved to loath them, so it probably did not take very long after humans learning the connection between sex and reproduction, for males to evolve to care about actual paternity.
And, since we now can quite reliably determine actual paternity, this really should show up in society’s laws and social expectations, but as yet, it does not.
In today’s society, there is nothing natural about Roman Catholic Natural Law.
We have, instead, the natural outcome of unrestrained female hypergamy, a mating system that is primarily lek based. Because of technological changes, Roman Catholic natural law can never be natural again, but we nonetheless have to socially construct institutions that stop female hypergamy and artificially and unnaturally impose monogamy on females.
Obviously, women only have as much power as men permit. The solution is to allow those males that likely have the best interests of the women at heart, husbands and fathers, to exercise that power that is the natural result of male characteristics, and require outsiders to butt out, which requires males to respect each other’s property rights in females. Rules on chastity and fidelity are then results of the natural law of property.
The Pauline concept of marriage as contractual imposes obligations on both parties to a marriage. From the natural law of contract, a marriage contracted for the purpose of children is necessarily durable. Neither party can cease to perform the duties of the marriage even if they are not feeling like it. And neither party can employ contraception or abortion or withhold reproductive sex except by the permission of the other.
Modern technology makes it possible to extend adolescence until a woman starts to run out of eggs. This outcome is undesirable, but there is no specific identifiable individual who has an interest in stopping it, except the father, so difficult to deem it illegal if the father permits it.
Rules for the transfer of authority from fathers to husbands are necessarily socially constructed, and not particularly natural. Obviously it is better for society and the family if a woman is under the authority of the man she is having sex with, rather than her father, so the laws should favor that first transfer of authority, and disfavor any subsequent transfer of authority.
A common eighteenth century system was transfer by elopement or patriarchal authority – the girl could transfer herself from the authority of her father to some man, or the father could transfer her. However, marriage without female consent means we don’t get all that good Pauline natural law of marriage, for that comes from the natural law of contract. So, a common eighteenth century system was the waltz, where a daughter was socially required by her parents to engage in sexy dancing with a parentally selected male. Which sexy dancing was very apt to lead to sex, which was deemed consent to marriage. So, marriage by forcefully manipulated consent. The only way to end parental authority was though female choice – which is, on the face of it, a dangerous system, since females notoriously are apt to make bad choices. But parents could, and did, apply a forceful thumb on the scales.
I have elsewhere argued for marriage without consent, in which fathers simply assign their daughters as seems best to them, and, in the event of the fatherless, the state acts, after the fashion of the early days in Australia. This is probably necessary when you have a very badly behaved female population, when one is arbitrarily and artificially creating family structures in a society where they have been entirely destroyed, which was the situation that the early Australian state found itself in. Probably the best system is that marriage by manipulated consent is normal and normative, with the possibility of backing it up by shotgun marriage in the event of demonstrated bad behavior, such as, for example, pregnancy.