My description of the natural law in Part I as the naturally knowable law of right and wrong is likely to prompt an objection. How can the idea of a moral law known to all people square with the undeniable fact of widespread moral disagreement between sincere and thoughtful people? If everyone can know, for example, that sex is right and good and humanly fulfilling only in marriage, why do so many people seem not to know it?
There are two interrelated reasons both addressed centuries ago by Thomas Aquinas. The first is that when we say the truths of the natural law are naturally knowable we are not saying that all its truths are equally easy to grasp. The more general truths such as that health, friendship, knowledge, etc., are good and to be pursued, and that their contraries bad and to be avoided, are easily seen and so readily affirmed by everyone. But moving from this level of generality to the more specific level of conclusions about what precise kinds of behavior constitute "contraries" to these basic human goods can be more difficult to see. To consistently get these more concrete conclusions right, our thinking needs the assistance of healthy culture, emotional self-mastery and clear philosophical reasoning, none of which has been prized very highly in the last decades. In consequence, people's thinking - Aquinas's second reason - gets clouded.
This movement from the general insights of the natural law to its concrete conclusions is waylaid when reason is corrupted by emotions, self-deceptions and rationalizations. When the corruption takes root in the collective thinking of a community, people's capacity to see some moral truths can be effectively lost. Take the issue of abortion, for example. Even into the 1960s, after the progeny of Margaret Sanger had been advocating for contraception for decades as necessary for the liberation of women from their state of biology-incurred domestic slavery, still the idea that a mother had a right to terminate the life of the child she'd conceived was universally repudiated: in the literature, in politics, even among the leaders of the feminist movement. Within a decade the idea was widely accepted, and within two the idea that abortion was a universal human right that all nations should be required to protect and facilitate was being championed at the UN. This shows how the corrupting of culture - by courts, political shysters, unscrupulous intellectuals and social revolutionaries - can impede the ability of many, including sincere and thoughtful people, to see what otherwise is rationally apparent.
What forces are powerful enough to lead to the corrupting of large numbers of people's ability to see moral truth? The problem is sizeable and complex, but I think we can identify three of the biggest offenders: (1) corrupt education, (2) corrupt media and entertainment and (3) corrupt laws. These three have conspired over the past half-century to change the epistemic conditions in which people conduct their moral reasoning.
In a culture that shames true masculinity and exalts a bastardized form of femininity, it is very difficult for boys and girls to grow up with a strong psychic and moral core.
In a culture that despises true religion, it is difficult for people to develop and sustain healthy and formative pieties.
In a culture that suffers from promiscuity mania, it is very difficult for people to inculcate the virtue of chastity.
In a culture that exalts and incentivizes a vision of adulthood that rises no higher than the stage of adolescent pan-selfism, it is difficult for people to commit themselves successfully to arduous lifelong relationships such as marriage.
In a culture that believes immediate self-gratification is a basic form of human flourishing, it is difficult for people to accept with resignation the sufferings they cannot avoid.
When our entertainment industry has been built by the Weinsteins of the world, our judicial system defaced by decisions like Roe v Wade, and our system of public education degraded by a militantly secularist mentality; when the voices of these powerful malforming forces are continuously bellowing in our ears, how can people find the mental space and quiet to reason soundly and consistently about moral matters? The fact that you and I and our children and everyone are struggling is what we'd expect. Some 2,500 years ago, Aristotle said that one who grows up in a corrupt culture neither has nor can easily acquire sound moral reasons. And Jesus says we shouldn't yoke ourselves to those who are hostile to our faith; communion with them is impossible (2 Cor. 6:14). Yet our laws, entertainment and education yoke us most intimately to these enemies of the natural law.
We all need to be instruments of cultural re-formation. We need lawmakers, lawyers and judges who revere the natural law; actors, directors, scriptwriters, fashion designers, financiers, etc. who are willing to produce a new generation of morally decent non-cheesy movies; and educators willing to teach consistently with the truths of the natural law.
Cultural re-formers. It sounds lofty but there's no way around it. Otherwise we are like those whom the poet Hesiod condemns as "useless human beings," those who neither understand what is good nor are capable of recognizing it when they see it.