Albert the Great, Alexander of Hales, Bonaventure, and others wrote about natural law (see Cunningham, Quinn). However, the most influential theological treatment was given by Thomas Aquinas in the Summa theologiae.
According to Thomas, reason directs human acts in view of some end. Action is commanded by the will, which wills the end, but for a command to count as law it must be in accord with some rule of reason (ST 1-2 q.90 a.1); thus law is from both the reason and the will of the lawgiver. Natural law is from the reasonable will of God (q.97 a.3); God’s reason, will, and law are identical with God himself (q.93 a.4 ad 1). The ultimate end to which reason directs action is the well-being of the whole community, the common good; every law, therefore, is ordered to the common good (q.90 a.2), and every law is ordered to friendship among those who share this common good (q.99 a.1 ad 2; a.2); the natural law fosters the friendship ofall mankind with God. Laws are made and promulgated by someone who has charge of the community. The natural law is promulgated by God’s inserting into the minds of human beings a natural capacity to come to know the natural law (q.90 a.4 ad 1). Laws include commands and prohibitions, and perhaps counsels and permissions. Whether Thomas thinks that law includes counsels is not certain: in one place (q.92 a.2; ad 2) he seems to say it does not, in another (q.100 a.2) that it may. Law can give permission by leaving some matters undetermined; according to Thomas, the Gospel law is a law of freedom because it leaves many things to the decision of the individual (q. 108 a.1). Natural law leaves some matters to be determined by human positive law (q.94 a.5 ad 3; 2-2 q.66 a.2 ad 1).
Thomas postulates an eternal law. In God there are ‘‘ideas’’ or ‘‘types’’ of created things (1 q.15), in creatures there are ‘‘participations’’ of these ideas. The eternal law is the type of God’s government of the universe (1-2 q.93 a.1),
The participation in human beings of the eternal law is the natural law. Whereas irrational nature is governed without knowing it by the eternal law, human beings can govern themselves consciously in accordance with this participation of the eternal law written into human reason (q.91 a.2). Natural law binds human beings in conscience (q.96 a.4). Natural law is morality (q.100 a.1, q.104 a.1).
The primary principles of natural law are the most basic general principles of practical reason. There is a plurality of indemonstrable principles of practical reasoning, but one is fundamental and the others are founded on it (fundantur, referuntur, reducuntur), though not by being demonstrated from it. Thomas draws an analogy between practical and scientific reasoning (q.90 a.1 ad 2, q.91 a.3, q.94 a.2): the fundamental principles of natural law are the counterpart in practical reasoning of the fundamental indemonstrable principles of scientific reasoning (cf. Aristotle, Anal. post. 1.3, 72b 18-25, Metaph. IV.4 1006a 5-12). A fundamental principle is known per se, that is, its predicate is part ofthe ratio (intelligibility) ofits subject. (Ratio here means not just a stipulative or verbal definition but an understanding of what something is.) Just as the first notion that speculative reason forms of something is that it is something, a being, so practical reason first apprehends what is to be done or brought about as a good. The first principle in practical reasoning, based on the ratio of good (‘‘that which all things seek’’), is that good is to be sought and done and evil avoided. Other indemonstrable principles are based on this first principle, in that various kinds of ends are naturally apprehended as good, namely those to which man has a natural inclination. (Inclinations belong to the appetitive faculty, the will; q.58 a.1.) Going from general to specific, natural inclinations can be classified as belonging to man as a substance, as an animal, and as a rational animal. Regarding man as a substance, there are precepts of natural law relating to the preservation of human life, regarding man as animal there are precepts relating to sex and the education of children, regarding man as rational there are precepts relating to the seeking of knowledge of God and participation in social life - forming a list reminiscent of, though not identical with, the content of natural law according to Cicero and the writers quoted by Justinian and Gratian. (For all this see q.94 a.2 and Grisez 1965.) Though the ordering of principles is from general to specific, it seems unlikely that preservation of human life is supposed always to override the others; Thomas does not discuss the possibility that in particular cases natural laws may conflict.
Secondary principles of natural law are derived as ‘‘quasi-conclusions’’ from the primary principles (q.91 a.3), again in an order from general to particular (q.94 a.4, a.6). The term ‘‘quasi - conclusions’’ (q.94 a.6, q.97 a.4 ad 3, q.99 a.2 ad 2), suggests that the derivation may not be strict logical inference. Thomas says that the most basic principles are exceptionless and are known to all, but practical reason is concerned with contingents, and the closer we come to contingent particulars the more often we encounter defects - one of the principles of Aristotle’s natural philosophy is that corruptible natures are defective in some cases. Derivative rules may therefore not apply in some circumstances. For example, in typical cases natural law requires “restitution of an article given in trust,’’ but that does not hold if the thing will be used to attack one’s country (q.94 a.4), or if it is a sword belonging to a madman (2-2 q.120 a.1). Adding conditions to the rule will not preclude exceptions, since the more conditions are added the greater the possibility that the rule will fail (1-2 q.94 a.4). Although the fundamental principles (including, as we will see, the Ten Commandments) are exceptionless and do not admit of dispensation, dispensation is possible from the more particular rules in unusual cases (q.94 a.5; q.97 a.4 ad 3; q.100 a.8).
The process of derivation continues into positive law. The two branches of human positive law, the law of nations and the civil law, are derived from natural law in different ways. The law of nations is derived, like the secondary principles of natural law, by inference (per modum conclusionis), the civil law is derived ‘‘by determination” (q.95 a.2). (It is natural law that we must not kill other people; if traffic is dense and fast moving, the duty not to kill may suggest that motorists should all drive on the same side of the road, but whether this should be the right side or the left is determined by the civil law.) Human law may bind in conscience (q.96 a.4), but human laws inconsistent with natural law are a corruption of law and do not bind morally (q.93 a.3 ad 2; q.95 a.2). Among the matters natural law leaves to be determined by human law is possession of external goods. The natural law permits human beings to use natural things (2-2 q.66 a.1), but (for reasons given by Aristotle, q. 66 a.2) in some circumstances it is best if some individuals control access to some things, and human law may provide for this by instituting property (q.66 a.2 ad 1).
The Decalogue (the Ten Commandments, Exodus 20:2-17) is a republication of some precepts of natural law. The natural law is a participation of the eternal law, which is divine, but there is also a ‘‘revealed’’ divine law, not promulgated by inscription in the minds of all mankind but promulgated to some human beings through messengers - Moses, the Prophets, the Apostles, etc. (q. 91 a.4); some of its precepts are positive laws (q. 99 a.4), but the Decalogue, promulgated through Moses, repromulgates some precepts of natural law. The Decalogue does not include the most basic principles of natural law, which are immediately obvious to all mankind and do not need republication, and on the other hand it does not include the more recondite implications of natural law (q.100 a.3, a.5 ad 1). The Ten Commandments are more particular than the most general principles, but they are (at a lower level, so to speak) general principles and can easily be seen by anyone; yet, because in a few cases human judgment regarding them can be perverted, they needed to be republished by divine revelation (q.100 a.11). The ‘‘first table’’ (the first three commandments) consists of precepts ordering mankind to the ultimate end, God; the second table consists of precepts regarding the order of justice among mankind (q.100 a. 8). (Commandments of the first table are self-evident to human reason informed by faith; q.100 a. 3 ad 1, q. 104 a.1 ad 3.) Just as the general principles of natural law are immutable, exceptionless, and indispensable, so are the Ten Commandments, which contain the very intention of the lawgiver (q.100 a.8). There have been cases when God directed or permitted action apparently contrary to one or other of the commandments, but these were not really contrary and were not really changes of natural law or dispensations from it (q.94 a.5 ad 2; q.100 a.8 ad 3). Some apparent dispensations were interpretations (q.100 a.8 ad 4). The explanation of other apparent dispensations is that because God is supreme lord and supreme judge, He can deprive some people of their life as punishment, or transfer their goods to others, or allot some woman to be some person’s wife, without violating the relevant precepts of the Decalogue.
Thomas’ account of natural law gives rise to many questions. How ‘‘good is to be sought and evil avoided’’ known per se - is it because ‘‘to be sought’’ is included in the ratio of good? If so, then ‘‘that which all things seek’’ cannot be an accurate statement of the ratio of good, since it implies no such prescription. What are the other selfevident basic principles? Thomas does not state them, but merely indicates their subject matter - for example, ‘‘whatever is a means of preserving human life and of warding off its obstacles belongs to the natural law.’’ How are the other basic principles ‘‘founded on’’ or ‘‘reduced to’’ the first principle, if not by being demonstrated from it? What are the derivative natural laws, and how are they derived? How do natural inclinations generate laws (q.94 a.2)? How is the list of natural inclinations drawn up - is man’s having these inclinations supposed to be known per se in the specified sense (i. e., that the predicate is included in the ratio of the subject), or in some other sense? Is the list ‘‘self-evident’’ merely in the loose sense that it will strike most people as obviously correct, ‘‘intuitively’’? Some common inclinations (e. g., selfishness, revenge) are not good: if they are ascribed to ‘‘sin’’ and not to nature, we must be able to distinguish between what is common and what is natural. Are all truly natural inclinations good, or do we regard as truly natural only those we recognize (on what grounds?) as good?
World History
