LAW OF NATURE
The moral law as universally binding on human nature, unchangeable in its essence, and knowable to all mankind. The law of nature is universally binding no matter how many people may violate it. Its universality of its observance. No matter how many or flagrant the transgressions, they do not change the value or extent of the law.
The law of nature is adaptable but not essentially changeable. There have been modifications adopted at one time or another in the law. On closer study, however, they are seen to be in fact changes in circumstances or in matters to which the law is applied. What cannot change is the substance of the law itself.
Also the law of nature can be perceived, however dimly, by every human being who has the full use of his or her reason. Certain social customs, clearly in opposition to this law, do not change the fact that it can be perceived by all. What such customs prove is that is that fallen human nature is prone to evil and need divine assistance as revelation even for a correct and generally available knowledge beyond the primary duties of the moral order. Obscured by passion and exposed to the moral pollution of secularist culture, human reason is weakened in its perception of what is right and wrong. Nevertheless its light is not completely extinguished, and besides, having access to revelation, the light of grace is also always available.