Catholic Encyclopedia hat geschrieben:Our knowledge of the law
Founded in our nature and revealed to us by our reason, the moral law is known to us in the measure that reason brings a knowledge of it home to our understanding. The question arises: How far can man be ignorant of the natural law, which, as St. Paul says, is written in the human heart (Romans 2:14)? The general teaching of theologians is that the supreme and primary principles are necessarily known to every one having the actual use of reason. These principles are really reducible to the primary principle which is expressed by St. Thomas in the form: "Do good and avoid evil". Wherever we find man we find him with a moral code, which is founded on the first principle that good is to be done and evil avoided. When we pass from the universal to more particular conclusions, the case is different. Some follow immediately from the primary, and are so self-evident that they are reached without any complex course of reasoning. Such are, for example: "Do not commit adultery"; "Honour your parents". No person whose reason and moral nature is ever so little developed can remain in ignorance of such precepts except through his own fault. Another class of conclusions comprises those which are reached only by a more or less complex course of reasoning. These may remain unknown to, or be misinterpreted even by persons whose intellectual development is considerable. To reach these more remote precepts, many facts and minor conclusions must be correctly appreciated, and, in estimating their value, a person may easily err, and consequently, without moral fault, come to a false conclusion.
A few theologians of the seventeenth and eighteenth centuries, following some older ones, maintained that there cannot exist in anyone practical ignorance of the natural law. This opinion however has no weight (for the controversy see Bouquillon, "Theologia Fundamentalis", n. 74). Theoretically speaking, man is capable of acquiring a full kowledge of the moral law, which is, as we have seen, nothing but the dictates of reason properly exercised. Actually, taking into consideration the power of passion, prejudice, and other influences which cloud the understanding or pervert the will, one can safely say that man, unaided by supernatural revelation, would not acquire a full and correct knowledge of the contents of the natural law (cf. Vatican Council, Sess. III, cap. ii). In proof we need but recall that the noblest ethical teaching of pagans, such as the systems of Plato, Aristotle, and the Stoics, was disfigured by its approbation of shockingly immoral actions and practices.
As the fundamental and all-embracing obligation imposed upon man by the Creator, the natural law is the one to which all his other obligations are attached. The duties imposed on us in the supernatural law come home to us, because the natural law and its exponent, conscience, tell us that, if God has vouchsafed to us a supernatural revelation with a series of precepts, we are bound to accept and obey it. The natural law is the foundation of all human law inasmuch as it ordains that man shall live in society, and society for its constitution requires the existence of an authority, which shall possess the moral power necessary to control the members and direct them to the common good. Human laws are valid and equitable only in so far as they correspond with, and enforce or supplement the natural law; they are null and void when they conflict with it. The United States system of equity courts, as distinguished from those engaged in the administration of the common law, are founded on the principle that, when the law of the legislator is not in harmony with the dictates of the natural law, equity (æquitas, epikeia) demands that it be set aside or corrected. St. Thomas explains the lawfulness of this procedure. Because human actions, which are the subject of laws are individual and innumerable, it is not possible to establish any law that may not sometimes work out unjustly. Legislators, however, in passing laws attend to what commonly happens, though to apply the common rule will sometimes work injustice and defeat the intention of the law itself. In such cases it is bad to follow the law; it is good to set aside its letter and follow the dictates of justice and the common good (II-II.120.1). Logically, chronologically, and ontologically antecedent to all human society for which it provides the indispensable basis, the natural or moral law is neither—as Hobbes, in anticipation of the modern positivistic school, taught—a product of social agreement or convention, nor a mere congeries of the actions, customs, and ways of man, as claimed by the ethicists who, refusing to acknowledge the First Cause as a Personality with whom one entertains personal relations, deprive the law of its obligatory basis. It is a true law, for through it the Divine Mind imposes on the subject minds of His rational creatures their obligations and prescribes their duties.