Lately I have been reading about natural law, learning specifically what it is and the ideas behind it, on an introductory level. Very basically, natural law is based on the idea that everything in nature is good (simply because they exist), and therefore things are good when they act according to their respective natures.
As an illustration, take a triangle (this and the squirrel example below are borrowed, loosely, from Edward Feser’s book The Last Superstition).
A triangle is defined as a closed plane figure having three straight sides. A triangle drawn on a drafting table using rulers and protractors will most likely have straighter sides than one drawn freehand in a moving vehicle. Thus we would say that the first is a better triangle than the second. Why? Because its straight sides and closed corners more closely adhere to the “standard” of triangularity that we hold in our minds, as compared with the freehand triangle, whose sides are slightly bowed and one of whose corners is not quite closed all the way.
Therefore, being a good triangle means conforming to the nature of triangles; and being a bad triangle means failing to conform to that nature. A triangle may be good in some ways and bad in others, i.e. having very straight sides but leaving one corner slightly open. The point is that you judge how good it is based on the standard, i.e. the nature, of triangularity.
I started with a non-living thing because I think it makes the point simpler to grasp. But the principle is the same with regard to living things, in terms of a thing being a better example of its kind the more closely it conforms to its nature. Thus a healthy squirrel with a nice, bushy tail and who scampers up trees and gathers nuts, is a good squirrel by virtue of doing things that conform to its squirrel nature; as compared with a squirrel with a rope-like tail who is too lazy to scamper up trees and gathers bottle caps instead of nuts, and so is not as good a squirrel as the first. This is not to say that he is a deliberately wicked squirrel, just that he is not as good at “squirreling” as the other one.
The case of human beings is more complicated (and I welcome correction wherever I get things wrong, since I’m still learning this stuff). This is because we can choose (to an extent) the extent to which we act in conformity with our nature: We are aware of our own nature and can reflect on it, and make deliberate decisions whether to, for example, mutilate our bodies for the purpose of squelching some of its natural functions. It is for this reason that there is a moral dimension to our behavior: We don’t act in accord with our nature necessarily, as animals do, who are unaware what their nature is and that there are alternatives to acting in accord with it. Squirrels can’t choose the extent to which they act in accord with the nature of squirrels, whereas people can choose whether to be good or bad examples of human nature.
This is the basic idea, I believe. There’s a lot more to it, especially since not every moral quandary has a clear answer spelled out in the book of human nature (or at least, we’re not always able to easily figure them out). The point is, though, that nature is a standard to which we can turn in order to discern what is good human behavior and what is bad, just as the nature of triangularity is a standard by which to measure whether and how one triangle is better than another; and the nature of a squirrel is one by reference to which we can look at a rat-tailed squirrel trying to eat bottle caps and say, “That is one weird squirrel”.
When you look at it this way, it’s kind of silly to call your dog a “bad dog!” when you catch him chewing on your slippers. Such behavior — destroying the property of others for our own enjoyment — is bad according to the morality which applies to self-conscious moral agents who know what “property” and “ownership” and useful things such as slippers are. But since chewing on inanimate objects is perfectly consistent with dog nature, and is in fact good for the dog since it cleans his teeth, we should really be saying “Good dog!”
The Canticle of the Three Young Men (Dan. 3:52-90) is a song of praise to God sung by three young men who have been cast into a fiery furnace. They call upon all creation to praise the Lord: Fire and heat, dews and hoar frosts, whales, fowl, beasts and cattle, are all called upon to bless the Lord and to “praise and exalt him above all forever”.
I was at a retreat this past weekend, and one of the priests who was giving a conference said, “How can ice and snow, seas and rivers, and so forth, bless the Lord? Well, by fulfilling their natures. Just like these orange trees out here, they praise and exalt the Lord just by being good orange trees, by being beautiful and bearing good fruit and sending forth that wonderful fragrance. The sun by rising over the mountains across the valley, praises the Lord, in fulfilling its nature, by sending rays of light into the valley, warming the earth and enabling the orange trees to grow and thrive and reproduce,” etc.
Thus things praise and exalt the Creator, and thereby do good, simply by acting each in accord with its nature. Makes sense to me!