The natural law is not just a philosophical theory; it expresses the common sense of plain people everywhere. This being the case, one would expect it to shine with particular brightness today, for the modern age is supposed to be the age of the common man. This is a myth. The modern age is not the age of the common man; it is the age of the expert.
The dominion of experts is understandable in specialized fields like computers and open heart surgery, but we make it the rule in every department of life. No one understands law but the lawyer, no one understands policy but the bureaucrat, no one understands ethics (supposedly) but the ethicist. There are no wise men any more, but only therapists. When all of life is dissolved into specialized fields, something is wrong.
Why has this happened? How has it come about that the common man has lost his place in the "age of the common man"? Perhaps the chief reason is philosophical.
Modern thought is much more elitist than ancient thought, though it talks a less elitist line. In both eras the great philosophers recognized that some men have greater understanding than others. The difference is that in ancient thought the ideal is the man of wisdom, whereas in modern thought the ideal is the man of expertise. Aristotle belonged to the old school. Though he pursued wisdom, he began all of his ethical reflections by considering what ordinary people think in all times and places. Even on those occasions when he considered the opinions of sages, they were the men whom ordinary people themselves recognized as sages.
Of course to begin with common sense is not the same as to end there. Indeed, in particular times and places the common sense of plain people can be corrupted. Even so, the wisdom of the philosopher lay mainly in his grasp of the deep presuppositions and remote implications of our universal common sense, not in something completely alien to it; what he tried to understand is what the common sense is getting at. Even when he offered corrections to common opinion, they were based on considerations that common opinion accepted; the correction was from within. The ideal was that when the philosopher had finished his work, the common man would say "Yes, that is what I wanted to say, but I didn't know how." This is also the deepest goal of medieval reflections on the Natural Law, and it is biblical too. There is, to be sure, a direct divine revelation which we cannot do without. And yet as St. Paul said, a law is written even on the hearts of the gentiles, however it may be suppressed.
By contrast, in the modern period the thread connecting the highest thoughts of the philosopher with the plain sense of the common man is stretched so thin that it finally breaks. The ancients thought common folk knew something, even if only in a general and confused sort of way. But in an incredible passion of hubris, Descartes thought that in the strict sense the common folk have no knowledge whatsoever, and that before himself, all philosophers have been in the same boat. The reason for this, he says, is that true knowledge is something certain, and no one before him has had certainty about anything; what they had was not knowledge, but merely opinion. To attain certainty, he proposes that all opinion be passed through a sort of certification engine of his own devising. The engine he devised was systematic doubt. Whatever can be doubted, should be doubted; no starting point should be accepted unless it literally cannot be doubted. This was the point of his celebrated line, "I think, therefore I am." In his own existence, he believed that he had finally found something that could survive his own intellectual meat grinder, for he could not doubt his own existence; if he was thinking, he existed! Starting there, he believed he could find other certainties.
Alas, his certification engine didn't work. I can doubt that there is thought; I can doubt that thinking requires a thinker; I can doubt anything whatsoever. So if certainty requires something that literally cannot be doubted, then the certification engine devised by Descartes has failed.
But even though his engine failed, his precedent stood. What the modern era decided that it had learned from Descartes is simply this: Nothing counts as real knowledge until certified by experts who have passed it through a certification engine -- be they lawyers, bioethicists, educational psychologists, or government bureaucrats. Which certification engine the experts use (and there are many) is no longer considered particularly important. What counts is that there is a certification engine, which no one but the experts understands.