Natural Law, Secular and Indeterminate
But to get back, let me give you a small taste of what I mean. It's pretty clear once you think about it. Though perhaps we are accustomed to natural law being fully determinate of all issues of right and wrong and also dependent upon the existence of God, neither is the case.
The natural law we're considering here is of course moral law. But take an analogy from biology where we may also speak of natural law. There are certain environmental conditions to which human beings are suited to thrive and others which cause them to do poorly. Just run through a variety of conditions and you'll see this. 4000 degrees Farenheit is inconvenient, as is zero degrees. Oxygen in the air is nice. When there's too little of it, well.... Also, there is a kind of diet which enables us to thrive. You can see that. Rocks and twigs are not so good. An all-meat diet isn't good, either. Etc.
Indeterminacy remains, though how much of it is an open question. How much greens to eat? Equatorial climate, or one more like that of France or Pennsylvania? The question closes up when you press the considerations further and look at anthropological and biological evidence for the suitability of certain environment and diet and the unsuitability of others. An array of different and approximately equally suitable environments and a similar array of diets remain. Yet the complete malleability of human nature as a theory drops out.
Now, is it preposterous to think that social arrangements, ethics, and character virtues are also tethered to human nature? Of course not. On the contrary, it is preposterous to think that human nature is suited to only certain diets and environments but is not a constraint on our choice of ethics and character virtues. This constraint, this tether, is natural law. It has some slack in it. There is more than one decent and admirable set of moral values which fits with natural law. Again, it is an open question how wide the options are. But the more you examine the question, the more it closes.
Let me throw out a value or two:
1. Each person ought to be allowed to act as he prefers and not be forced by others to act in accordance to their preference.
2. Violation of #1 is a forfeiture of one's own protections under #1. In other words, if you force others to act in accordance with your will, you may rightly be stopped.
3. Self-reliance and industry are good, and sloth is bad.
4. One ought to help members of one's community who do not violate principle #1 but who fall into dire straights through no fault of their own.
5. Failure to distinguish between dire straights fallen into through no fault of one's own and dire straights created by sloth and foolishness is bad. One ought not to help the foolish and slothful.
There are caveats to all of these principles, of course. There are no moral rules, but only summary rules of thumb. But you get the gist.
How about your values? Are they likely to suit human nature? Or do you suspect they likely violate natural law, while you look away? Do you feel lucky where others have failed repeatedly?
But there is more than human nature working in natural law. There is an analytical core to it. Wanton cruelty is immoral. Small kindnesses done for innocent people are good. These are so by definition. The terms "right", "wrong", "moral" and so forth have meanings which are not utterly inelastic. For example, a bowling ball can't be "what is right." Nor can it be immoral. The point is that there is an analytical definition of "rightness" which constrains morality as well as human nature does. Natural law, then, is the fact that the meanings of moral terms and the kind of creatures we are constrain how it is good for us to live.
In any event, these facts about natural law are so even if God does not exist. Imagine a world in which He does not exist. In that world, these facts are so. Imagine another world in which these facts are so and there is a God who holds human nature constant while attempting to make it the case that these facts about natural law no longer obtain. He fails. Q.E.D. Even God can't make cruelty good and liberty worthless. He didn't make them, respectively, bad and valuable in the first place.
The upshot is that the dismissal of natural law as hopelessly absolutist (i.e., committed to absolute determinacy in all areas of morality) or hopelessly committed to divine command theory is a non-starter.
By the way, progressivism is wedded to that non-starter, just as a matter of fact. If you're a lefty, you need to reform your position to say that socialism and statism are consistent with natural law and even more adherent to it than the alternatives. Good luck with that. Principle #1 is a tough customer. And when you look at the prosperity that has issued from this liberty, you really have problems. Why don't you consider abandoning your desire to be a puppet master, a designer of society? You're in violation of natural law. You might want to reflect on what motivates you. It isn't the plight of poor people. After all, you don't give all your wealth above the poverty line to charity, now, do you? You don't volunteer at the soup kitchen 15 hours a week, now do you? What, then, would drive you to embrace values that fly in the face of natural law?