Here’s another factor that makes for difficulty in confidently judging whether this or that is clearly in accordance with the natural law, or is a breach of it. The way in which God accommodated himself to the primitive and uncivilised attitude of his chosen people, the nation of Israel. These accommodations concerned the revealed law of God, which was tempered to the people on account of their rudeness. The most notable of these concerns divorce, as Jesus taught, which was permitted due to the hardness of the hearts of the people.
Or take, for instance, polygamy. As far as I am aware, polygamy is not forbidden in the Old Testament. And to go no further back, King David, a man after God’s own heart, and King Solomon, the wisest man that ever lived, were polygamists. David had Bathsheba and Michal as wives, Solomon was the husband of Naamah and of a daughter of Pharoah, and later on hundreds of wives and concubines. There is no suggestion, I think, that these two kings ever suffered a pang of conscience over the matter. And Solomon was condemned not because of the number of his wives, but because they were foreign, and so led him astray.
It is only in the New Testament, in the teaching of Jesus, which is monogamatic, and of Paul, who teaches that Christian marriage is a symbol of and a shadowing of Christ’s relation to his church, his bride, that polygamy is ruled out. But by this stage we are moving decidedly outside the field of natural law, pure and simple. As John Murray puts it,
The only thesis that appears to me to be compatible with these data is that polygamy and divorce (for light cause) were permitted or tolerated under the Old Testament, tolerated in such a way that regulatory provisions were enacted to prevent some of the grosser evils and abuses attendant upon them, and tolerated in the sense that openly condemned and censured with civil and ecclesiastical penalties, but that nevertheless they were not legitimated. That is to say, these practices were basically wrong; they were violations of a creation ordinance, even an ordinance which had been revealed to man at the beginning. (Principles of Conduct p.16)
Not a greater good defence, but a greater evil avoidance defence.
Now supposing that the Christian, in his secular, work-a-day world, wishes to argue against polygamy, how can he utilise the natural law to do so? How do we explain God’s toleration, if that is the correct word, of polygamy in the Old Testament?
Murray goes on
How could this be? How could God allow his people, in some cases the most eminent of the Old Testament saints, to practice what was a violation of his preceptive will? It is a difficult question….[Our Lord] tells us explicitly that for the hardness of their hearts Moses suffered the Israelites to put away their wives, but that from the beginning it was not so (Matthew 19: 3-8; Mark 10: 2-9)…..there is no good reason why the same principle should not be applied to polygamy. (p.17)
[As David Wright showed, this principle of divine accommodation and forbearance was a notable feature of John Calvin’s interpretation of the Pentateuch. See ‘Calvin’s Pentateuchal Criticism: Equity, Hardness of Heart, and Divine Accommodation’ (Calvin Theological Journal, April 1986), and further writing cited there.]
Our question is rather different from Murray’s. It is this. How could God allow his people, in some cases the most eminent of the Old Testament saints, to practice what was a violation of the natural law, if indeed monogamy is a constituent part of that law? We might say that if the Lord was prepared to temper the demands of his revealed law in respect of the creation ordinance of monogamous marriage so that even the greatest saints of the Old Testament were polygamous and seem to have no bad conscience in being such, how can we clearly detect, unaided by special revelation, the boundaries of the natural law? If what counts as a practice in accordance with natural law respecting marriage were to allow for the widespread Old Testament practices of polygamy and concubinage, as well as divorce, were it not for express, revealed teaching to the contrary, how can the mere widespread acceptance of a practice (though with only special revelation clearly against it) be evidence for that practice being in accordance with the natural law? If polygamy is widespread in a society, what is the natural law argument against the practice?
In his A Biblical Case for Natural Law, (2006) David VanDrunen warns that
looking to natural law as the common moral standard in the civil kingdom demands limited and sober expectations…Sinful human beings will struggle to know how to make appeals to natural law in a relatively helpful and persuasive way….The civil kingdom, regulated by natural law, is severely limited in what it can attain, but Scripture gives us no reason to expect more from it. (p.40-1)
No doubt cautions are appropriate. These look to be cautions about the strength with which society will embrace the norms of the natural law. But our concerns here are rather different, namely, how can those who seek to argue on the basis of natural law alone be sure what the boundaries of the natural law is? Of course in practice the issue is not as clear cut as this. Because the second kingdom is presently influenced not only by the natural law, but by the operation of a residue of beliefs which have been influenced by special revelation in one form or another, by ‘traditional Christian values’ as they are sometimes called, the influence of which still lingers. The tide of faith may be in retreat in certain places, but the beach stays wetted by it for a time.
Even if we hold that the contours of the natural law are provided by special revelation. Jesus teaches that divorce is a concession due to the hardness of hearts. (So Matt. 19) So is divorce a concession as regards the natural law too? And polygamy was a concession under the OT? It is not even mentioned in the NT. May it be a concession still? The incentives offered by Christians to society at large while living in the second kingdom may be various, not only appeals to the natural law, but also reliance on the vestiges of the days when the Christian in our society was more widespread. All that is true. But our question remains, what are the boundaries of the natural law, and how do we know this nowadays?