Today, when many people think of “the law,” they see it as, at best, a necessary evil to maintain order—or at worst, as a harmful imposition. This contrasts directly, however, with the Biblical notion of a law that is to be loved: “I love thy law / Seven times a day I praise thee / for thy righteous ordinances…The law of thy mouth is better to me / than thousands of gold and silver pieces…I delight in thy law” (Ps 119:163-164, 72, 70).
This radical difference stems from what people perceive as the foundation of the law. While many today see the law as founded upon the Constitution, upon a “do no harm” morality, or upon the best guesses of politicians, for much of human history such a law would have been considered no law at all. In his Summa Theologiæ (Prima Secundæ, questions 90-96), St. Thomas Aquinas gives a summary of what this older—and possibly better—notion of the law looks like.
St. Thomas starts by giving a definition of the law that almost anyone could agree with: “Law is a rule and measure of acts, whereby man is induced to act or is restrained from acting.” He explains that, for human deeds, this “rule and measure of acts” is the power of reason. Unlike the actions of an animal, which are not conscious and therefore cannot be morally “good” or “bad,” human acts are measured against an objective standard of reason. Having established this, St. Thomas specifies three main categories of law.
Eternal Law is first, not only in importance but also in order of contingency. Since “the whole community of the universe is governed by Divine Reason,” it is this Reason that is the principle and source of all other kinds of law. Without Divine Reason pervading every crack of the universe, everything would be unintelligible and impossible to organize. Since the Eternal Law is for “the whole community of the universe,” this law includes every other law within itself, making it the highest, as it encompasses the perfect moral relation toward everything.
Next is Natural Law, second in the order of importance and contingent on the Eternal Law. This law is “nothing else than the rational creature’s participation [in] the Eternal Law.” All things are subject to the Eternal Law and participate in it some way, and the special participation the rational creature has in the Eternal Law is called the Natural Law.
This rational creature participates in the Eternal Law in two ways. First, it shares with all created beings “respective inclinations to their proper acts and ends” because the Eternal Law is “imprinted on them.” God designed the whole universe like an artist, and His reason for creating this artwork is visible in every individual part of His creation. This is what St. Paul means when he says, “What the law requires is written on their hearts” (Rom. 2:15).
Second, rational creatures can access the Eternal Law in a particular way because they can use reason to tend towards its mandates, through observing their own nature and the nature of the things around them. For example, we can quite easily reason, despite popular opinion, that the marriage act is ordered towards procreation, and that acting actively against that end would constitute a violation of the Natural Law.
Lastly, there is human law, the least important and third in the order of contingency. Human laws are promulgated by a government (or other proper authorities) and are precepts of the Natural Law applied to particular situations for different countries, times, and people. It seems that the reason most people are so suspicious of the idea of the law is because they conflate all law with the human law—which is the least perfect kind. This is because, unlike the Eternal Law that is weaved into the very fabric of the universe, human laws are subject to change “on account of the…condition of man.” In addition, human laws are not true laws at all if they violate the Natural or Eternal Laws.
When our eyes are opened to the higher forms of law, along with their unchangeable notion of justice and their pathway to happiness, it becomes much more obvious how the psalmist can exclaim:
Oh, how I love thy law!
It is my meditation all the day…
How sweet are thy words to my taste,
sweeter than honey to my mouth!
Through thy precepts I get understanding;
therefore I hate every false way.