MEDIEVAL THEORIES OF NATURAL LAW

John Kilcullen

Abstract: Natural law was a key concept in medieval moral and political theories. Originating in ancient Greece, it came to medieval thought mainly through the canon and civil law texts. Commentators on these texts tried to solve various difficulties, especially regarding the justification of property. Thomas Aquinas, Duns Scotus, William of Ockham and many other theologians discussed natural law, especially in relation to God”s commandments.

(A shorter version of this essay has been published in Springer Encyclopedia of Medieval Philosophy.)

In medieval texts the term ius naturale can mean either natural law or natural right; for the latter sense see the article “Natural Rights”. Ius naturale in the former sense, and also lex naturalis, mean the universal and immutable law to which the laws of human legislators, the customs of particular communities and the actions of individuals ought to conform. It is equivalent to morality thought of as a system of law. It is called “natural” either (a) because it is taught by natural instinct, i.e. some capacity innate in human beings, or (b) because it is accessible to “natural reason”, i.e. to personal reflection independent of any special revelation from God (such as the Christian faith claims to be) and independent of the moral authority of other human beings; or for both reasons.

Medieval writers referred to human law as “positive law”, “custom” or “convention”. The positive law of a particular community was called “civil law” (there is no contrast here with criminal law); often the term referred especially to the civil law of the Romans. The term “law of nations” (ius gentium) seems equivalent in some Roman law texts to natural law, or perhaps to part of natural law; in medieval texts it usually means the laws common to the positive law of all, or most, human communities. (The boundary between natural law and the law of nations was never very clear.) Natural law was also distinguished from “divine positive law”, which is not knowable by natural reason but is notified to some human beings, and not to others, through special messengers (Moses, the Prophets, the Apostles, etc.).  

The concept of natural law originated in ancient Greece and came to the middle ages mainly through Aristotle, the Bible, Cicero and Augustine, and especially through the Roman and canon laws. During the middle ages many theologians and lawyers made some use of the concept. In this article only a few of the main writers will be discussed.

Ancient sources

Sophocles’ Antigone appealed to the “unwritten and unfailing” statutes of divine justice as an authority superior to human law, constraining her to risk the death threatened by human law (Antigone, lines 450-460). Among the Greeks the contrast between nature and convention was commonplace, and many of the Sophists (at least in one phase of their thinking—see de Romilly, pp. 176-187) saw selfishness as natural and saw justice, which restrains selfishness, as conventional. Plato presents the sophist Thrasymachus (Republic 343b-344c) and the otherwise unknown Callicles (Gorgias 482c-484c) as arguing that justice is a set of conventions that constrain the self-interested action that nature prompts, conventions that an intelligent person will break through when possible. Plato has Glaucon report that many people argue that, although conventions generally serve self-interest by reducing conflict, they will be disregarded by a person following nature if he can do so in secret or otherwise with impunity (Republic 358e-360d). Plato’s Socrates, on the other hand, argues that justice is an eternal reality, not a matter of human convention, and that it is always to a person’s true advantage to act justly, even when injustice could be committed in secret or with impunity. Aristotle took the same side in the debate.

The works of Sophocles and Plato were unavailable in medieval Europe, but from the 1260s the Latin translations of Aristotle’s Politica and Ethica Nicomachea were widely read. A leading concept in these works is nature. According to EN 1097 b22-1098 a19, human nature is such that “the good” for each individual consists in acts of virtue carried on in a context of friendship (the friend being “another self”, EN 1166 a31, 1170 b7), and not in the possession and enjoyment of the things for which Thrasymachus and Callicles thought it natural to compete (though Aristotle acknowledges that some moderate possession of such things, shared with friends, is necessary to the good life). Nature is best seen not in the primitive but in the fully developed. The good life in its most developed form is life in a city (polis); hence the human being is by nature a “political” animal (Pol. 1252 b30-1253 a3). Politics is concerned with friendship among citizens and with justice in the broadest sense, which is complete virtue in relation to other persons (EN 1130 b25). “Of political justice part is natural, part legal,—natural, that which everywhere has the same force and does not exist by people’s thinking this or that; legal, that which is originally indifferent, but when it has been laid down is not indifferent” (EN V.7, 1134b18-22). The latter he describes as “legal and conventional”, “just by virtue of convention and expediency”, just “by human enactment”, like weights and measures. Similarly, in Rhet. I.13 he distinguishes between “universal” and “particular” law: particular law is law “which each community lays down and applies to its own members”—i.e. “civil law” in medieval terms—, whereas “universal law is the law of nature…, binding on all men, even on those who have no association of covenant with each other”; and he quotes from Sophocles’ Antigone. In Pol. I.5, 1254a 19, in what may be an echo of a debate the Sophists opened up, Aristotle asks: “Is not all slavery a violation of nature?” (Pol. I.5, 1254a 19). In a dialectical exploration (though later he seems to regard the conclusion as proved), he argues that some human beings are by nature slaves. But “there is a slave or slavery by law as well as by nature. The law of which I speak is a sort of convention” (Pol. I.6, 1255a5). Aristotle assumed the naturalness of virtue and saw justice and politics as being based on nature, with conventions or human enactments determining matters indifferent by nature. This harmonises well with medieval theories of natural law.

Another source of medieval ideas on natural law was the Bible. Readers of the Bible would of course gather that God’s law rules human actions. Much of the Bible is concerned with divine positive law, but in Paul’s Letter to the Romans there is a passage that was taken as referring to natural law: “For when the Gentiles, who have not the law”, that is, the law of God as found in the Bible, “do by nature those things that are of the law”, they “show the work of the law written in their hearts, their conscience bearing witness to them”, etc. (Rom. 2:14). “The law” here is “the Law”, i.e. the Law of Moses, so the passage suggests that the Law of Moses contains the natural law. Hence Gratian’s remark (see below) that “the law of nature is what is contained in the Law and the Gospel”.

Paul may have been influenced by the ideas of the Stoics. The Stoics followed Plato and Aristotle in holding that virtue is natural. According to the Stoics, the good life is to live “in accordance with nature” or virtue. By nature they meant not only human nature, but the whole of nature, the cosmos. A virtuous person lives in accordance with “the universal law, which is the right reason pervading everything and identical to Zeus” (Long and Sedley, vol. 1, p. 395). Cicero was a transmitter of Stoic ideas. His Republic had been lost, but a passage from it on natural law was known to medieval readers through quotation by Lactantius: “There is indeed a true law, right reason, congruent with nature, applying to everyone, constant, everlasting, which calls us to duty by commanding and deters from crime by forbidding… To alter this law is not right, it is not permitted to repeal any part, it is impossible to abrogate it entirely; we cannot be absolved from this law by senate or people; we do not need Sextus Aelius as explainer or interpreter. There will not be one law at Rome, another at Athens, one now and another later; but one law, everlasting and immutable, will bind all peoples at all times… Of this law God is the author, judge and legislator” (Long and Sedley, vol. 2, p. 428.) In De inventione Cicero wrote that the beginnings of justice “proceeded from nature, then certain things because of their usefulness became customary; later the things that came from nature and were approved by custom were sanctioned by fear of the laws and religion. The law of nature [naturae ius] was not begotten by opinion but was implanted by some force in nature” (or as he says at II.xxii.65, “which some innate force brought to us”). (De inventione II.liii.160-1).

A lengthy extract from De inventione, including the passage just quoted, is included in Augustine’s De diversis questionibus 83 (q. 31). Elsewhere Augustine often refers to natural law (as in PL 37 col. 1574, Ennaratio in Psalmum CXVIII Sermo XXV.4) or, more often, to the eternal law (see Chroust, 1944; Crowe, pp. 62-7). However, he does not give any elaborate treatment of the subject, but merely repeats, incidentally to some other topic, ideas that were already commonplace. For example, in De libero arbitrio I.v.11-vi.15 there are a number of texts on the distinction between eternal and temporal law, which Thomas Aquinas quotes in his own discussion of law (e.g. ST 1-2 q.91 a.1 sed contra), but these do not go beyond Cicero and are incidental to the discussion of other matters. Thomas quotes also from De vera religione xxx.56; the text quoted is the culmination of a general Platonist argument that what is mutable is judged against an eternal standard. Other medieval authors also quote Augustine on the eternal law. For example, Gregory of Rimini (vol. 6, p. 235) quotes the following: “Sin is an act, statement or wish contrary to the eternal law; the eternal law is the divine reason or will of God, commanding the preservation of the natural order and forbidding its disturbance” (Contra Faustum, XXII.27). But what follows in Contra Faustum is not further explanation of the eternal law, but a discussion of sin as a violation of order. It seems fair to say that if medieval theologians had not already been alerted to the topic of natural law by the civil and canon law texts, they might not have made much of Augustine’s references to natural law.

Justinian and Gratian

What is now known as the Corpus iuris civilis, including the Digest (a collection of excerpts from earlier Roman legal writers, such as Gaius and Ulpian) and the Institutes, was published in the sixth century under the name of the Emperor Justinian. The Digest was used as a text book in the schools of civil law that developed in Bologna and elsewhere from the late eleventh century. Schools of canon law (i.e. the law of the western Church) also came into existence, using as text Gratian’s Concord of Discordant Canons, commonly referred to as the Decretum, written sometime during the first half of the twelfth century. The Digest and the Decretum both begin by distinguishing kinds of law, including natural law. Under the influence of these text books, natural law became a central topic in European thinking about law, government and morality from the twelfth century onwards.

In Justinian’s corpus there is a disagreement about natural law, or at least some confusion of terminology. Sometimes “natural law” and “law of nations” are distinguished and contrasted: thus slavery was introduced by the law of nations, whereas “according to natural law all persons were born free” (Dig. 1.1.4). But in other texts the terms seem interchangeable. The law of nations (or, according to the parallel passage of the Institutes, the natural law) “was brought forth with the human race itself” (Dig., 41.1.1; cf. Inst., 2.1.11). The law of nations is established by natural reason (Dig. 1.1.9), which is the source of natural law. “By natural law we obtain the ownership of some things which, as we have already stated, is called the law of nations . . . Therefore . . . all creatures that exist on the earth, in the sea, or in the air, as soon as they are taken by anyone, immediately become his property by the law of nations, since whatever formerly belonged to no one is conceded by natural reason [which establishes natural law] to the first person obtaining possession of the same” (Inst., 2.1.11-12 ). The terms had different origins: originally “law of nations” seems to have been a term for rules applied by the Roman courts to non-Romans, whereas the term “natural law” seems to have been borrowed from the philosophers (Buckland, pp. 53-4). In various places in the Digest and in the Institutes there are traces of the philosophers’ conception, according to which the law of nature is the law that applies to human beings as rational, equivalent to the universal and everlasting law of reason: “Natural laws, which are equally observed among all nations, established by divine providence, remain always firm and immutable” (Inst. 1.2.11); “Ius is said in a number of senses; in one way that which is always equitable and good is said to be ius, as is the ius naturale” (Dig. 1.1.11, Paulus). If the law of nations is distinguished from natural law, what is the distinction? Ulpian says that natural law is what nature teaches all animals, whereas the law of nations is used by human beings (Dig. 1.1.1.3 and 4). This seemed unsatisfactory, since it suggested that animals follow law, which most medieval readers thought only rational beings could do, and it might seem to suggest that human beings are bound by the same laws (for example, in matters of sex) as animals follow.

Whether the law of nations and the natural law are identical or different affects the status of two important institutions, slavery and property. According to Dig. 1.1.4 (quoted above), the two laws are not identical, and slavery belongs to the law of nations and not to natural law. Might this be true also of property? The civil law texts say that property belongs to the law of nations, but in these contexts the law of nations and the natural law are not contrasted. According to one text, the law of nations includes reverence toward God, obedience to parents and country, self-defence, government, property, contracts of various kinds (Dig. 1.1.2-5). According to another text, property, dominia distincta, i.e. appropriation of a thing to some individual or group to the exclusion of others, was established by the law of nations (Dig., 1.1.5, 41.1.1 and 3). According to another text, property was established by the natural law “which is called the law of nations” (Inst., 2.1.11-12). Generally civil lawyers held that property exists by natural law, but Gratian quotes a text in which Augustine says that property exists by human law (dist. 8 c.1, cols. 12-13): since medieval civil lawyers could not ignore the opinion of Augustine, and canon lawyers and theologians could not ignore the civil law, the status of property became a problem.

Gratian’s Decretum makes no mention of a natural law common to mankind and other animals, and the law of nations is treated as distinct from, and subordinate to, the law of nature. According to Gratian the law of nature is a divine law found in the Law (i.e. the law of Moses) and the Gospels (I, dist. 1, d.a.c.1; Friedberg, vol. 1, col. 1). The essence of the law of nature, according to Gratian, is to treat others as we wish them to treat us; as Jesus says (Matthew 7:12), “this is the law and the prophets”. Gratian’s account of law is given mainly through quotations from the sixth century ecclesiastical writer, Isidore of Seville, who seems to be condensing and normalizing what he found in the Roman law writers. According to Isidore, human “civil” law consists in customs or human enactments (c.8, col. 2), which differ from one community to another (c.1). Natural law, on the other hand, is common to all peoples and is everywhere held by the instinct of nature, not by any enactment (c.7, col. 2). The law of nations is the law that is used by nearly all peoples (c.9, col. 3); it seems to belong within the category of human law, as a nearly universal body of customs or enactments. It is clear that Isidore regards natural law and the law of nations as distinct, since he gives two different lists of their content. Natural law includes “the union of man and woman, the generation and rearing of children, the common possession of all things and the one liberty of all, the acquisition of those things that are taken from air, sea and sky, the restitution of an article given in trust or money loaned, and the repelling of force with force” (c.7). The law of nations includes “the occupation of territory, building, fortifying, wars, captivities, slaveries, rights of restoration, alliance of peace, armistices, the inviolability of ambassadors, the prohibition of marriage with an alien” (c.9). According to Gratian natural law is supreme: “In dignity the natural law prevails absolutely over custom and statute. For anything accepted by custom or contained in writing should be held null and void if it is opposed to natural law” (dist.8, d.a.c.2, col. 13). Custom must give way to truth and reason (c.4 and 5, col. 14).

Problems arising from the law texts

The relationship between the law of nations and natural law clearly needed to be sorted out, and there were also problems about property and slavery. Isidore’s text as quoted by Gratian says that natural law establishes “the common possession of all things”, but also that it allows “the acquisition of what is taken from air, land and sea” and requires “the restitution of an article given in trust or money loaned”. The common possession of all things seems inconsistent with the acquisition and restitution of property. There was also conflict between natural law and human law. Gratian and Isidore say that by natural law all things are common, and according to Augustine property exists by human law: if natural law invalidates any contrary human law, as Gratian says it does, how can human law establish property? According to Isidore, natural law establishes “the one liberty of all”. How then could human law establish slavery? Medieval commentators had no doubt that property and slavery were legitimate: “thou shalt not steal” is one of the Ten Commandments; New Testament texts imply the legitimacy of slavery (Ephesians 6:5, Colossians 3:22, Philemon, 1 Peter 2:18). If property and slavery are contrary to natural law, why are they not therefore “null and void”?

One solution was offered by Rufinus, one of the early commentators on Gratian. According to Rufinus (pp. 6-7), natural law includes commands, prohibitions and demonstrationes. By demonstratio (which can perhaps be translated “indication”) natural law points out what is fitting or shows what is good (“demonstrat quod convenit”, “bona esse ostendit”). According to Alexander of Hales (vol. 4, p. 348), by “demonstration” Rufinus means “advice” (consilium). Demonstrations include the “one liberty of all” and “common possession of all things”. Unlike commands and prohibitions, demonstrations can be set aside for a good reason—to do so in some circumstances may serve purposes recommended by natural law (e.g. the enslavement of criminals may serve peace and justice). Demonstrations are not merely “licit” or “permitted”. Natural law not only permits but recommends certain things, such as freedom and community, without commanding them.

Others offered a solution based on the idea of permission or concession. They suggested that property and slavery exist by the permission of the natural law. (Tierney has discussed permissive law in many places: see Tierney, 1997, index “Natural Law, permissive”; Tierney, 2001; Tierney, 2002, p. 399ff). But the idea of “permissive” natural law needs clarification. In civil law a positive or explicit permission may be needed to correct other laws (“notwithstanding law X, so-and-so is permissible”). Corrective provisions will not be needed in natural law, which is not the imperfect work of human legislators—if (as Thomas Aquinas and others held) natural law consists in self-evident principles and their implications, then the implications are simply what they are, though admittedly our understanding of natural law may need to be corrected and the correction might conveniently be formulated as a permission. Implicit permission may be given, however, by the silence of the law—i.e. when the law includes no command or prohibition on some matter—under the general understanding that what is not prohibited is permitted. Thomas Aquinas (ST 1-2 q.94 a.5 ad 3) and many who followed him held that the question whether goods should be common or private is left open by natural law to be decided by human beings—natural law does not command or prohibit either. Property would have been legitimate also in the state of innocence. Community belongs to the natural law “negatively” as some later writers put it, meaning that it belongs to natural law in that natural law permits it. However, as Suarez realised, it is not enough to say that natural law merely permits either community or property, freedom or slavery; rather, community and freedom are the preferred state for mankind, to be set aside only for good reasons, pertaining to natural law “positively”. (See Suarez, II.xiv.16-19, vol. 4 p. 33ff.) Suarez in effect returns to Rufinus’s notion of “demonstrations”, things that are recommended though not commanded.

The Summa fratris Alexandri put forward another possible solution. (Alexander of Hales was one of the founders of Franciscan theology. The Summa attributed to him contained a good deal of material contributed by members of his school.) This Summa reported Rufinus’s distinction between precept and “demonstration” (Alexander of Hales, vol. 4, p. 348), and the distinction between precept and permission as stated by Hugh of St Victor (pp. 351-2), but also suggested that natural law may give different precepts for different circumstances. (This is based on Augustine’s explanation of how the same God can be the author of the Old Law and of the New.) Adam’s sin introduced a great change of circumstances, and in view of this difference natural law prescribes the one liberty and community of goods for the state of innocence but for the fallen state prescribes slavery (for some) and property (p. 348). The leading Franciscan theologian of the next generation, Bonaventure, adopted a similar position (Bonaventure, 2 Sent., dist. 44, a. 2, q. 2, ad 4, vol. 2, p. 1051). Similarly, Scotus held that community of goods is highly consonant with natural law for the state of innocence, property for the fallen state (see below). Ockham followed Alexander and Bonaventure (see below).

Some civil lawyers in the later middle ages (e.g Bartolus, Paulus de Castro) distinguished two divisions of the law of nature, namely (a) the law of nature that applies to all animals (cf. Ulpian) and (b) the law of nature that applies specifically to human beings, and two divisions of the law of nations, namely (c) the “primeval” law of nations, brought forth with the human race itself (cf. Inst., 2.1.11), and (d) the “secondary” law of nations, which grew up gradually, at first in the form of custom, as the numbers of mankind increased: (b) is identical with (c), and this is the law of nations referred to in many of the Roman law texts; (d) is identical with the law of nations mentioned by Isidore, and it is distinct from the natural law in either sense, being a branch of human positive law. This was their attempt to sort out the confusion in Roman law terminology. They also tried to answer the questions whether, and how, property exists by the law of nature by suggesting that property in moveables (e.g. consumables) is basic and natural, whereas property in immovables (e.g. land) developed in the secondary law of nations in imitation of property in movables: thus one kind of property is natural, the other conventional. All of this was later taken over by Grotius in De iure praedae (see Kilcullen 2001b, p. 905ff; on Bartolus see editor’s note in Suarez, vol. 4 p. 130, n. 274). Whether property exists by natural law, the law of nations, civil law or divine positive law continued to be debated into the eighteenth century.

Thomas Aquinas

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. Thomas’s treatment of natural law forms part of a treatise on various kinds of law. Almost three quarters of this treatise is devoted to the revealed divine law (the Old Law, i.e. the Jewish Law, and the New Law, i.e. the Christian Law), and more than half of it to detailed commentary on the ceremonial and judicial precepts of the Old Law.

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 wellbeing 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 of all 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).

Like Augustine, 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. I.3, 72b 18-25, Metaph. IV.4 1006a 5-12). A fundamental principle is known per se, i.e. its predicate is part of the ratio (intelligibility) of its 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 derivation of secondary principles may not be understood by everyone (q.94 a.4). Some implications of the basic principles may be obvious to everyone, at least when pointed out, but some are not grasped except through experience and study, and many people will need to be taught the less obvious implications by someone wiser than themselves (cf. q.100 a.1). No one can be ignorant of the fundamental principles, but it is possible for the knowledge of more particular rules to be clouded, for example by vice (q.94 a.4, a.6; q.99 a.2 ad 2).

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).

Thomas classes the law of nations as human positive law, but since it derives from natural law by way of conclusion it seems hard to distinguish from the more particular principles of the natural law, which are also quasi-conclusions of the principles of natural law. A possible distinction is suggested by some Roman Law texts defining natural law as the law that applies to all animals. In Thomas’s view irrational animals are not guided by any law other than the eternal law (1-2 q.91 a.2 ad 3; q.93 a.5). However, he says that natural law includes laws (for men) corresponding to the inclinations men share with other animals, while the law of nations consists of laws corresponding to inclinations specific to men as rational (2-2 q.57 a.3; 1-2 q.94 a.3 ad 2). In replying to an objection arguing that the law of nations is not human law but natural law, Thomas does not come down on either side: the law of nations is in a way natural because derived from natural law by an inference not remote from its premises, but it is distinct from natural law, “especially from the natural law that is common to all animals” (q.95 a.4 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, re-promulgates 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’s account of natural law gives rise to many questions. How is “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 self-evident basic principles? Thomas does not state them, but merely indicates their subject matter—e.g. “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? Thomas gives too few illustrations. (There are a few: see q.95 a.2 on the derivation of “one must not kill”, and q.100 a.6 and a.7 ad 1 on certain duties including gratitude.)

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? (For other senses see Thomas’s commentary on Aristotle, Anal. post. I, lect. 10.) 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?

The end the law aims at is the common good; but although the good of individuals often harmonises with the common good, there are surely cases of conflict. Do the individual’s natural inclinations seek the individual’s good, e.g. self-preservation, or are they oriented to the common good, e.g. the survival of most members of the community? (On this see Eschmann.)

Thomas says that although basic moral principles have no exceptions, derivative laws do, because the closer we come to contingent particulars the more often we encounter defects. But since all moral judgments bear ultimately on contingent particulars, why are not all moral principles subject to exception? What happens when two basic principles conflict—or can that never happen? Thomas says that negative commandments always bind but affirmative commandments not always (q.100 a.10): but the most basic principles of the natural law seem to be affirmatives, so how are they exceptionless? Thomas argues that not everyone is obliged (affirmatively) to procreate (2-2 q.152 a.2 ad 1); why is it then that, as modern Thomists usually say, every sex act must be open to procreation?

Thomas was followed in his account of natural law, as in many other things, by late medieval and early modern Dominicans and Jesuits, for example by Vitoria, De Soto, Molina, Lessius, and Suarez. Since the late 19th century there has been a revival of interest, arising especially from attempts to find a natural law basis for the moral teachings of the Catholic Church on sex and medical ethics. Thomas Aquinas’s own treatment of certain topics of sexual morality can be found in Summa contra gentiles III.123-125 and ST 2-2 q.154.

Duns Scotus

According to Scotus, the term “law of nature” has a strict sense and a broad sense. In the strict sense, the laws of nature include practical principles known from their terms (nota ex terminis) and conclusions that can be inferred evidently from those principles. In a broad sense, the laws of nature include practical truths that are consonant (consonans) with the law of nature in the strict sense (Wolter, pp. 262-3; on what Scotus may mean by “consonant” see Ragland). Laws of nature in the strict sense hold always, for whatever state or condition human beings may live in (p. 264-5). They are prior to any act of will, even God”s—the divine intellect must recognise their truth and the divine will must will in accordance with the intellect’s recognition of their truth. They admit of no exceptions; not even God can dispense from them. What they command is good in itself apart from the command, what they prohibit is wrong in itself apart from the prohibition.

Scotus distinguishes between commandments of the first table of the Decalogue, which formulate duties we have toward God himself, and commandments of the second table, which regulate our conduct toward other human beings. The command to keep holy the Sabbath day is not part of natural law in the strict sense, and the other two commandments of the first table belong to strict natural law only if given a negative formulation, as precepts not to hate God and not to love as supreme any but the true God. (Scotus holds that only negative commands belong to natural law in the strict sense.). The commandments of the second table are natural law only in the broad sense, and God has power to set them aside. God’s power is limited only by the impossibility of his doing anything self-contradictory (p. 256). To set aside a practical truth nota ex terminis, or one evidently inferred from such a truth, i.e. a natural law in the strict sense, would involve self-contradiction. But God can without any contradiction revoke any of the commandments relating to the good of our neighbours.

Against this it might be argued that love of God implies love of our neighbours, since if we love God we must wish others to love him, and wishing for that is to love them; the commandments of the second table therefore follow evidently from natural law in the strict sense and are therefore natural laws in the strict sense. Scotus rejects this argument for several reasons (pp. 282-4): first, because the duty to love God is affirmative and therefore not part of strict natural law—the strict duty is not to hate God, and we can fulfil this duty without wishing anyone else to love God. Second, because God may not wish to be loved by everyone, e.g. not by those whom he has not predestined to salvation. Third, because even if we do want our neighbour to love God, that does not imply any of the commandments of the second table—for example, we can want our neighbour to love God without having any duty not to kill our neighbour. God has revealed that he wills us to love our neighbour in ways that go beyond anything that can be strictly inferred from the natural law obliging us to love God; the second table expresses that will, it does not spell out strict implications of natural law.

These are arguments for rejecting Thomas’s doctrine that not even God can dispense with the commandments of the Decalogue. Whether God has in fact done so is another question. Thomas referred to a number of occasions on which God apparently dispensed with one or another of the commandments (ST 1-2 q.94 a.5 obj. 2). Scotus repeats these examples, and argues that they show that God has in fact dispensed. To the objection that the command “thou shalt not kill” does not fully express the intention of the legislator, i.e. that it is only an approximate statement of the obligation, Scotus answers that precision is not the issue. Granted that the commandment does not intend to forbid every killing, the question remains: Can God’s permission in a particular case make licit an act that, apart from this permission, would be really forbidden, by the commandment precisely formulated? If so, then God can dispense from the Decalogue, just as he replaced the Old Law with the New, just as a legislator can replace one positive law with another; if not, then he cannot dispense. If Abraham had killed his son that would really have been a violation of a commandment in its true intention, which proves that God has dispensed from the commandment “thou shalt not kill”. (In this argument Scotus seems to envisage the first paragraph of ST 1-2 q.100 a.8 ad 3, in which Thomas points out that the commandments need to be accurately interpreted. But Thomas goes on to make another point, namely that God’s supreme lordship and judgeship implies power to deprive a person of life or reallocate property, etc., so that the apparent dispensations turn out not to be dispensations really. At a later point Scotus accepts this argument in relation to one of the examples, namely the despoiling of the Egyptians (Wolter, p. 287).) There are other examples of dispensation. God gave the Jews permission for divorce and gave the patriarchs after the flood permission to practice polygamy, each of which was a dispensation from the commandment forbidding adultery (pp. 292-3, 303).

God also revoked the law that prohibited appropriation in the state of innocence (pp. 280-1, 312-5.). (The law against appropriation does not belong to the Decalogue, but according to Isidore (above) natural law includes “the common possession of all things”.) After the fall God revoked the prohibition against appropriation; some time after that, human law established the institution of property, and God’s law then prohibited theft. Scotus explains (p. 312-3) that the original prohibition and later permission of appropriation served the same ends, namely peace and sustenance, under different circumstances. In the state of innocence community of goods served those ends best, in the fallen state appropriation does; if goods had remained common in the fallen state the physically weak would have suffered from the greed of the powerful. That the physically weak should be protected, that people should live together peacefully, and that there are many morally weak persons who care mostly about themselves and not much about others, all seem obvious. The institution of property in the fallen state is very consonant with those suppositions, though not implied with strict necessity. Scotus comments that perhaps it is thus with all positive laws: they do not follow with strict necessity from the underlying principles, but only as very consonant with them (p. 281).

If they are not nota ex terminis and not demonstrable, how do we come to know these natural laws in the broad sense? If they have their binding force only from God’s legislative will, how do we know his will? Scotus himself does not address the problem. Interpreters have suggested several possible answers: (1) Perhaps natural laws in the broad sense are known only through the revelation of God’s will made to Jews and Christians. But against this, it seems that all human beings recognise, or ought to recognise, that stealing, adultery, etc. are wrong. So (2) perhaps there was a “primitive revelation” made to the whole human race. Both of these answers leave it difficult to see how these laws can be said to be natural. Perhaps (3) these precepts are known naturally not by rational analysis but intuitively—the precepts are, as Paul said, written in the human heart (“In order to know what is morally good, we must know what God wills. But it does not follow that we must know what God wills under that description”; Williams, p. 74, and cf. p. 93). On this account Scotus’s theory is an intuitionism in which rational intuition of strict natural law principles nota ex terminis is supplemented by some other kind of intuition bearing on natural law in the broad sense.

Unlike Thomas, Scotus in his account of natural law makes no reference to natural human inclinations. An appeal to natural inclinations would have been inconsistent with Scotus’s view of freedom of the will and the contingency of creation. According to Scotus, the will is free in the sense that it has an instantaneous “power of opposites”, i.e. that when the will chooses something, it simultaneously has full power to choose the opposite (Ordinatio 1, dist. 38-39; Scotus, Opera omnia, vol. 6, p. 417-9). (Ockham accepted this theory with an important modification, viz. that the will has power to choose the opposite only at a later instant; but it can do that even if meanwhile nothing in the universe has changed; Ordinatio, dist. 38, OTh, vol. 4, pp. 580-1.) According to Scotus, human decisions, and God”s, are not determined by thoughts, dispositions or other causes. This implies that God is not bound by any rules or laws in his decisions about creation. God is free to create human beings with certain natural inclinations, without being bound to issue them with any commandments, and without being bound to command them in ways that further their natural inclinations. Human will, according to Scotus, has two "affections", an affectio commodi, which is a tendency to seek objects of natural inclination, and an affectio iustitiae, a tendency to choose to do what is right and good because it is so (Wolter, p. 178-9). It is the affectio iustitiae that constitutes human freedom. It sets us free to disregard our natural inclinations and to choose to follow God’s commandments instead, whatever they may be, even if they do not suit our inclinations.

William of Ockham

According to Ockham (Quodl. II q.14, OTh, vol. 9, p. 177), positive morality consists of laws that oblige a person to seek or avoid things only because they have been ordered or prohibited by a superior, but there is a “non-positive” morality consisting of laws that direct human acts apart from any command of a superior. Non-positive morality consists of directives that are either fundamental principles per se nota or laws deduced from such fundamental principles together with experience. (The reference to factual experience differentiates Ockham’s position from that of his predecessors.) Non-positive morality is the natural law (3.2 Dial., 1.5, 1.10). Scotus also recognized a non-positive morality, but it contains only precepts relating directly to God. The extent of Ockham’s non-positive morality is not clear, but it seems to include a larger number of precepts, especially in view of his recognition of natural laws “of the third kind”.

There are three kinds of natural law (3.2 Dial., 3.6). The first (elsewhere called “absolute” natural law, 3.2 Dial., 1.11) consists of natural laws that hold always, everywhere, in all conditions of mankind; no necessity excuses disobedience (3.1 Dial., 2.20), they are immutable and no dispensation from them can be given (except by God, as we will find): for example, “Do not commit adultery”, “Do not lie”. The second kind are the laws to be observed by those who make no use of custom and human legislation, laws that would have been observed in the state of innocence and would still be observed if everyone lived according to natural reason or divine law: for example common possession. The third kind are laws gathered by evident reasoning from the law of nations or another law or from some act, divine or human, unless the contrary is decided on with the consent of those concerned. The third kind are natural laws “on supposition”. On the supposition of the fall from innocence, and on the supposition that human law has established the institution of property as a way of reducing conflict and other evils of the fallen state, natural reason will infer that one must not use something belonging to another without the owner’s consent. The law of nations consists in, or includes, natural law of the third kind (3.2 Dial., 3.7 near the end). Ockham’s doctrine of three modes seems to be a development of ideas of Alexander of Hales, Bonaventure and Scotus (see above), and likewise resolves the conflicts found in Gratian’s extracts from Isidore.

Ockham mentions a large number of natural laws. Apart from the laws on supposition, which are perhaps innumerable, he mentions many natural laws of the first kind: “‘do not worship strange gods’, ‘do not commit adultery’, ‘do not bear false witness’, ‘do not lie’ and the like” (3.2 Dial., 1.10)—i.e., the Ten Commandments; “the will ought to conform itself to right reason”; “every blameworthy evil is to be avoided” (vol. 9, p. 178); “when something does me good and you no harm, it is fair that you should not prohibit me” (OND 66.47-9, p. 581); “help is to be given to a poor person in extreme need” (8, p. 424); “everything dictated by right reason on account of a due end (and so of other circumstances) is to be done”; “every good dictated by right reason is to be loved” (vol. 6, p. 425). However, he does not pause to explain how these various laws are per se nota or derivable from principles per se nota together with experience. For example, he says that anyone who deliberates will see that an innocent person should not be killed, but he does not describe the deliberative process: “For if, on some occasion, someone is tempted to kill an innocent person who never did harm, then immediately, if he wills to deliberate, even briefly, about whether he should kill him, it will occur [to him] that he should not kill him” (3.2 Dial., 1.5).

Ockham does not follow Scotus in giving a lower status to the second table of the Decalogue, but unlike both Thomas and Scotus he says that God may make dispensations from any of the Ten Commandments (even commandments of the first table). Ockham seems to hold that one of the principles of non-positive morality is that God is to be obeyed, and that this principle overrides the others when there is conflict. From this it seems that God can make exceptions or give dispensations from any natural law, either by allowing an occasional exception or by replacing the current moral law: “If they are simply commandments of natural law, no case should be excepted for any necessity or utility whatever, unless God specially excepted some case—as, notwithstanding the commandment of purely natural law about not knowingly killing the innocent, God made a special exception in commanding Abraham to sacrifice his son” (3.1 Dial., 2.24); “I say that . . . hate, theft, adultery and the like . . . could be done by the wayfarer even meritoriously if they were to fall under a divine precept, just as now in fact their opposites fall under divine precept . . . But if they were thus done meritoriously by the wayfarer, then they would not be called or named theft, adultery, hate, etc., because those names signify such acts not absolutely but by connoting or giving to understand that one doing such acts is obliged to their opposites by divine precept” (OTh, vol. 5, p. 352). To love God, or at least the negative, not to hate God, is a principle of natural law; love of God is necessarily a good act and the most basic of good acts. Nevertheless, the natural law that God is to be obeyed overrides even the law that God is to be loved—if God commanded an act of hatred of God, the commandment would bind. “Everything that can be a right act on the way [i.e. on earth], also [can be right] in the fatherland [i.e. in heaven]. But to hate God can be a right act on the way, for example if it is commanded by God, therefore in the fatherland” (vol. 7, p. 352). (Suarez argues cogently that it is impossible for God to give such a command: II.xv.5, vol. 4 p. 50.)

The overriding force Ockham gives to divine commandments has led some historians to classify him as a “voluntarist”, implying that he holds that morality is whatever God wills it to be (cf. Copleston, vol. 3.1, p. 115ff). (These historians also classify Scotus as a voluntarist, despite his view that the prohibition on hating God is independent of God’s will.) If this is Ockham’s position, it is open to the well-known objections against divine-command theories of morality (see for example Mill, vol. 10, pp. 27-29). Suarez attributes this position to Ockham, referring for evidence to Ockham’s 2 Sent. q. 19, ad 3, ad 4 (Suarez, II.vi.4, vol. 3 p. 81). In the modern edition this text is q. 15 (OTh, vol. 5, pp. 352-3, partly quoted above). Its main point is that God could, without doing any wrong himself, cause a human being to do some act normally wrong; it also asserts that for a human agent God’s commands have overriding force. But this does not justify Suarez’s classification of Ockham as a divine command theorist. In Ockham’s view, the obligation to obey God”s commands is an obligation of natural law that overrides other precepts of natural law, but that it overrides them does not imply that they hold, when they do, only because they are commanded by God. Perhaps his view is that an act contrary to natural law, such as adultery, is wrong in itself but the wrong of disobedience to God would be greater, so that a person might be obliged by divine command to commit adultery, which would then, under the circumstances, be right. (See Kilcullen 2001a.) Ockham himself seems to reject the intellectualist/voluntarist dichotomy: “In God the act of will and the act of intellect and the will are in every way the same, nor is the act of will more distinguished from the will than the will is distinguished from the will” (OTh, vol. 3, p. 329). “And when it is said that ‘the intellect is the noblest power’, I concede it; and similarly the will is the noblest power, because the power that is the intellect and that which is the will are in no way distinguished a parte rei or a parte rationis . . . because they are names signifying the same, connoting precisely distinct acts, namely of understanding and of willing” (vol. 1, p. 402; cf. vol. 5, p. 441). Ockham states explicitly (see above) that there is a non-positive morality independent of the will of a superior, and there are places where he distinguishes between things wrong in themselves and things wrong because prohibited (3.1 Dial., 2.20). However, it must be said that Ockham did not make his position clear. (For an account of the role of reason in Ockham’s moral theory see McGrade, 2006, pp. 66-70; on divine command and rational ethics in Ockham’s moral theory, see McGrade1999.)

Gregory of Rimini

Though modern historians classify them as voluntarists, Scotus and Ockham say that natural law in the strict sense, or “non-positive morality”, is independent of God’s will. According to Scotus, propositions which “are true by reason of their terms . . . would be true even if, to assume the impossible, no act of willing existed” (Wolter, p. 275). Gregory of Rimini went further and said that the necessary truths of morality are independent also of God’s intellect—if human beings existed but God did not, adultery would still be wrong.

To the question why he says that sin is against right reason, rather than against divine reason, Gregory answers that he says this “lest it be thought that sin is precisely against divine reason and not against any right reason…, and lest it be thought that something is sin not because it is against divine reason as being right, but because it is against it as being divine. For if, to assume the impossible, the divine reason or God himself did not exist, or his reason was in error, still, if someone acted against angelic or human right reason or any other (if there be any), he would sin. And if there existed absolutely no right reason, still, if someone acted against what some right reason, if it existed, would say should be done, he would sin” (Gregory, p. 235). Many things are sins of themselves and not just because they have been prohibited; even if no divine command were ever given, a person could know and judge that such things are not to be done. “If anyone acts solely against the natural law or against the right judgment of reason” (Gregory assumes that these are equivalent), “certainly he would sin, though, if he were to have with this a superadded precept, he would sin further” (Gregory, p. 238, emphasis added). Since God forbids what is already wrong, there is a double sin. (We see here a forerunner of the later distinction between “philosophic” and “theological” sin.)

In answer to objections, Gregory says that a moral proposition can be expressed either in the indicative or in the imperative mood; for example, when Paul says, “Every fornicator etc. has no inheritance in the kingdom of Christ and God” (Rom. 1:32), this indicative statement is equivalent to an imperative forbidding fornication etc. (Gregory, p. 241). (Suarez presents this as a distinction between “indicative” and “preceptive” law (Suarez, vi.3, vol. 3 p. 79), whereas Gregory means that the same law can be formulated either in the indicative or in the imperative.) Thus indicative statements of what is right and wrong are commands in a broad sense (though in a narrower sense only imperatives are commands). But the distinction between indicative and imperative is not essential to Gregory’s point, which is that (whether stated in the indicative or the imperative) the precepts of natural law forbid acts wrong in themselves even apart from any divine command, but, since God does exist and does command obedience to these precepts, anyone who sins against natural law sins further against God.

Francisco Suarez

De legibus ac deo legislatore (1612) by Francisco Suarez is a detailed treatment of the topics of Thomas Aquinas’s treatise on law, upholding Thomas’s positions against ideas that had been put forward in the meantime. Grotius and other early modern writers show acquaintance with Suarez, whose learned discussion takes account of many works by medieval theologians and jurists. His work thus forms a bridge between medieval and early modern theories of natural law. Of the many matters he discusses we will examine only a few. (All references are to De legibus II.)

Distinction between law of nations and natural law

Suarez attempted to answer a question that Thomas Aquinas had left unclear, viz. how the ius gentium differs from the law of nature. Ockham suggested that the law of nations, or much of it, consists of laws of nature of the third type (above); some civil lawyers identified the law of nature specific to humans with the primary law of nations; others suggested that the natural law consists solely of the self-evident principles and the ius gentium of all conclusions drawn from the principles. Suarez rejects these theories (vii.2-4, vol. 3 p. 110ff; viii.9, vol. 3 p. 134-5; xix.4, vol. 4 p. 129). One of his key distinctions is between things forbidden because they are wrong and things wrong only because they are forbidden. (The distinction has many antecedents, e.g. in Augustine, in Aristotle; see Suarez vi.11, vol. 3 pp. 92-4. See also Plato, Euthyphro 10a; Aristotle, EN V.7, 1134b18-22; Thomas Aquinas, 2-2 q.57 a.2 ad 3; Ockham, Quodl. II q.14, p. 177, 3.1 Dial., 2.20.) According to Suarez, natural law consists in the totality of laws that prohibit acts wrong in themselves rather than wrong because prohibited (xix.2, vol. 4 p.126). It includes both the fundamental self-evident principles and all the conclusions, applicable to any state of mankind, that can be drawn from them by necessary inference—not merely the more obvious conclusions, but absolutely all the necessary implications (xvii.8, vol. 4 p. 109). The law of nations is quite distinct from natural law. It prohibits or requires things that would not be wrong or obligatory if it did not make them so (xvii.9, vol. 4 pp. 110-11). It is a branch of human positive law (cf. Thomas, ST 1-2 q.95 a.4). It consists in the unwritten laws common to all or almost all nations (xix.6, vol. 4 p. 131-2). It differs from the civil law in that its rules are less specific, less a matter of choice between more or less equally satisfactory arrangements, closer to the rules of natural law—this is how Suarez tries to salvage Thomas’s statement that the law of nations differs from the civil law by being derived from natural law by way of conclusion, rather than by way of determination. As Suarez puts it, the ius gentium “is said to be constituted by way of conclusion and not determination because from the force of the law of nations it does not receive complete determination in particular but is brought in, in general terms, by way of inference, inference not simply necessary but so suitable (conveniens) to nature that it is made at nature’s instigation (as it were)” (xix.3, vol. 4 p. 128).

Suarez recognises, and was apparently the first to do so, that the law of nations includes a body of laws regulating relations between states (xix.8-9, vol. 4 p. 134ff). The human race always forms a moral and political unity, an international community with a common good furthered by a body of laws. Some obligations relevant to international relations are imposed by natural law—for example, if a treaty is made, the parties are obliged by natural law to observe it. But it is the law of nations that obliges nations to be willing to make treaties. Similarly the law of nations includes a requirement to receive ambassadors and respect their immunity, permission for citizens to enter into contracts with people of other nations, laws of war that are additional to natural law requirements, and so on. However, the ius gentium is not absolutely universal and immutable, and civil law is not subject to it (xv.10, vol. 4 p. 55; xx.6-7, p. 145-7).

Suarez does not reject Ockham’s laws “on supposition” (above), but he regards them as natural law and not also part of the ius gentium: “There are many things in the law of nature that do not oblige and have no application except on some supposition” (xvii.9, vol. 4 p. 109-110). As Suarez envisages it, the natural law contains from eternity and immutably all the rational requirements that may apply to any situation at any stage of human history. Before Eve was created Adam could not commit theft, but “Thou shalt not steal” was already a law of nature, awaiting application once the institution of property had been established. “It is one thing to speak of the existence (so to speak) of precepts, another of their actual obligation or exercise. Therefore, though a state can call for the use of one precept and not another, nevertheless the law of nature is always the same and includes the same precepts, because they are either principles or conclusions necessarily inferred—therefore they have a necessity that does not fail in any state” (viii.9, vol. 3 p. 134). According to Suarez natural laws may depend on human action in that they have no application until human beings do something (e.g. make some law), but they are laws of nature eternally (xiv.7, 11-12, vol. 4 p. 23, 27-9).

Dispensations from the natural law

Suarez uses the same distinction between a law and the object to which the law applies to explain some apparent dispensations from natural law. God is not only legislator but also supreme lord and judge. As legislator he cannot make exceptions to natural law, but in some other capacity he may be able to effect a mutatio materiae, i.e. a change in the object or matter to which the law applies, so that it no longer applies. Thus God, as supreme lord of all things, was able to transfer property from the Egyptians to the Israelites, so that their taking things that had previously been the property of the Egyptians was not theft (xv.18-20, 22, vol. 4 p. 62ff). The same distinction explains Thomas’s remark (above) that the closer we come to contingent particulars the more likely are exceptions to the natural law. According to Suarez the more contingent and particular the matter the more likely it is that what might have seemed an object to which a certain law applies may really not be. Uncommon cases may show the need to refine a rule that has been formulated inaccurately (xiii.6-8, vol. 4 p. 9ff). For example, the madman demanding return of his sword does not really come under the natural law requiring restitution of an article given in trust, if that law is accurately formulated. Similarly papal annulments and God’s permission of polygamy to some Old Testament patriarchs show that the formulation of laws concerning marriage needs to be refined. Marriage has a relation to the conservation of the human race, which is ultimately the concern of the author of nature. More accurately formulated, natural law says that a marriage cannot be dissolved by private decision, such as the will of the parties, but this leaves it open to dissolution by divine or public authority. Similarly, in some circumstances God can permit polygamy to conserve the human race or some part of it, without any violation of natural law (xiv.20, vol. 4 p. 38; xv.28, p. 73). (On the other hand, there can be no dispensation from the natural laws against fornication and lying, i.e. there is no refinement in the formulation of the rule and no possibility of mutatio materiae; xv.5, pp. 50-1; xv.28, p. 73.)

Another approach, turning on the distinction between ius in the sense of law and ius in the sense of a right (see article “Natural Rights”), is needed to explain adequately how natural law may seem to require community of goods in the state of innocence and property in the fallen state. Suarez rejects Scotus’s arguments and holds that neither community nor property was necessary in either state—the most that can be proved is that in one or the other state one was useful and the other disadvantageous or unnecessary (xiv.13, vol. 4 p. 30). Following Thomas, Suarez says that natural law leaves it to human decision to choose between community and property, and also between liberty for all and slavery for some. But a difficulty arises: if natural law does not require liberty or community, then it would seem that a tyrant could reduce the rest to slavery and seize all goods without violating natural law. In reply, Suarez calls on the notion of a right. Originally human beings had a natural right to liberty and to the use of common goods; the tyrant would be violating those rights. But then, how can slavery and property ever have been established legitimately by human decision, if these institutions violate original rights? Suarez answers that people can voluntarily surrender rights and the commonwealth (but not a private person setting up as tyrant) can for good reasons abolish certain rights: the establishment of property or slavery did not violate any eternal law of nature, but merely abolished, possibly for good reason, original rights (xiv.16-19, vol. 4 p. 33ff).

Suarez tries to clarify the idea that while negative precepts are exceptionless, positive precepts are not. This idea perhaps originated with Augustine’s attempt to explain how a Christian is not in all circumstances bound “to turn the other cheek”: according to Augustine such precepts bind to a preparedness to act in a certain way in the appropriate occasion, but not in all circumstances (Letter 138 ii.13). In Scholastic authors the idea was expressed by the dictum that positive precepts bind “always, but not for always” (semper, sed non pro semper), whereas negative precepts bind always and for always. (See Thomas Aquinas (above) and Scotus (above) and Ockham, 1 Dial., 4.26, 6.39, etc.) According to Suarez, a positive precept will be binding on certain necessary occasions, and on those occasions it is as binding as a negative (xv.14, 20, 29; vol. 4, pp. 59, 64, 75).

Morality and divine commandments

Suarez also tried to clarify the relationship between morality and God’s commands (vi.3-5, vol. 3, p. 79ff)  He presents his position as a “middle way” between the “divine command” theory he attributes to Ockham (above) and the line of thought represented by Gregory of Rimini (above). During the sixteenth and seventeenth centuries there was controversy over whether natural law stems from God’s will or from his intellect. Earlier writers did not take either side. According to Augustine, “the eternal law is the divine reason or will of God” (above). Thomas Aquinas refers to God’s “reasonable will” (above). Scotus and Ockham say that natural law in the strict sense, or “non-positive morality”, is independent of God’s will. According to Gregory of Rimini the necessary truths of morality are independent also of God’s intellect—if human beings existed but God did not, adultery would still be wrong. 

A contemporary of Suarez, Gabriel Vasquez (see Suarez v.2, vol. 3, p. 60), held a position like Gregory's. According to Vasquez, “A sin is evil of itself prior to any prohibition, whether that prohibition be imperative or indicative, created or divine” (St. Leger, p. 131). “The formal nature of sin does not lie in the fact that an act is contrary to the judgment of reason, but rather in the fact that it is inconsistent with rational nature” (p. 131). “If we should concede, which is indeed impossible, that God did not judge as he does now, and if there remained in us the use of reason, sin would remain (p. 132). “Things are not evil because they are judged to be so by God. Rather they are so judged because they are such of themselves.…The first natural law in rational creation is, therefore, nature itself, as rational, for this is the first rule of good and evil” (pp. 133-4, emphasis added).

Against these views Suarez insists, with Thomas Aquinas, that natural law is commanded by God’s reasonable will. Against Gregory's position Suarez objects (vi.1, 2; vol. 3 p. 76ff) that such theories imply that the natural law is not a law (since law implies the command of a superior) and is not divine (if it would remain even if there were no God). He does agree (in fact, this is one of his key ideas) that some acts or omissions are wrong in themselves, apart from any command (vi.11, vol. 3 p. 92); but he argues that since there is a good God who exercises providence over his creation, it must be that he commands rational creatures not to do anything intrinsically wrong (vi.8, vol. 3 p. 89; vi.23, vol. 3 p. 105), and this command imposes a moral obligation additional to the “(so to speak) natural” evil the act has in itself (vi.12, vol. 3 p. 94ff). Even if we do not know by revelation that God commands the moral law, we can infer that morality must have been commanded by God from God’s existence and providence, which are knowable by natural reason. By the natural light, i.e. by use of natural reason without revelation, human beings can understand that some acts are evil in themselves, that a good God exists and is provident, that God therefore must forbid what is evil in itself, that acts evil in themselves are therefore sins. (vi.24, vol. 3, p. 106-7). Suarez answers Gregory and Vasquez (as he understands them): “The natural law does not merely indicate evil, but actually obliges us to avoid it; it does not merely represent the natural disharmony (disconvenientiam) of an act or object with rational nature, but it is also a sign of the divine will prohibiting it” (vi.13, vol. 3 p. 96). Suarez agreed with Gregory and Vasquez that there is a double obligation, that a wrong act violates reason as well as God”s command. The difference is that Suarez reserves the term natural law for morality as commanded by God, whereas Gregory and Vasquez refer to nature itself, or to morality, as natural law, even apart from any divine command.

Grotius seems to have taken note of this discussion (see Chroust 1943; St. Leger, p. 132ff). There are clear echoes in De iure belli ac pacis: “What we have said [about natural law] would still be in point even if we should grant, what we cannot without great wickedness, that there is no God, or that He bestows no regard upon human affairs” (Prol. 11). “Natural law is a dictate of right reason indicating that moral turpitude or moral necessity characterises some act from its suitability or unsuitability with rational nature itself, and consequently that such act is commanded or forbidden by God, the author of nature” (De iure belli ac pacis I.1.10). (Suarez would not have been quite satisfied with that: in his view, God commands the natural law not precisely as “author of nature” but as provident; see vi.2, vol. 3 p. 77.)

Another author apparently influenced by this discussion was Samuel Clarke, the leading exponent of what historians call the “rationalist” tradition among British Moralists (see Raphael, vol. 1, pp. 212-4). “All intelligent creatures… ought to obey the same rule according to the law of their nature; even though it could be supposed separate from that additional obligation, of its being the positive will and command of God” (p. 213, emphasis added). Clarke’s rather vague language of fitness and unfitness (p. 192) is found also in Vasquez (sin is “inconsistent with rational nature”) and occasionally in Suarez (e.g. “goodness or malice arise from the consonance or dissonance of the act with rational nature”, vol. 3 p. 76). When Suarez uses such language, it must be interpreted in the light of Thomas’s scheme of self-evident principles and necessary conclusions—i.e., dissonance with nature means inconsistency with some self-evident practical principle or some conclusion.

After the Middle Ages

Medieval natural law theories belong to the genus of theories that suppose that morality is “objective”, i.e. that moral standards are independent of the opinions of any human individual or social group. Specifically, natural law theories (1) undertake to derive the standards from basic principles per se nota, and (2) claim that the standards are laws sanctioned by God. Other attempts to conceptualize an “objective” morality have differed on both these points. Aristotle, for example, seems to draw up his list of virtues intuitively and relies on the intuitions of a virtuous person to guide choice in particular cases, and Aristotle’s God in no way concerns himself with human beings and issues no commands. The chief weakness of medieval natural law theories relates to the first point. Medieval writers failed to present the self-evident basic principles clearly enough to make it possible to judge whether they really are per se nota, and they failed to show in detail how other precepts of the natural law can be demonstrated from the basic principles (or from the principles together with experience, as Ockham suggested). The rational derivation of morality remained merely a project lightly sketched out.

Nevertheless, the theory, or at least the terminology, of natural law continued into the seventeenth century, for example in the writings of Grotius, Locke, Cumberland and many others. The “Natural Law and Enlightenment Classics” series (general editor Knud Haakonssen) demonstrates the continuing vitality of the natural law tradition into the eighteenth century (see also Buckle, 1991a). During the nineteenth and twentieth centuries it was eclipsed by other conceptions of morality, but has been revived more recently by Germain Grisez, John Finnis and others. The moral doctrine of the Roman Catholic Church, especially concerning sex and medical ethics, is still today often presented in terms of natural law.

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Bibliography

Primary sources:

Alexander of Hales, Summa Theologica, Quarrachi: Collegium S. Bonaventurae 1924-.

Anal. post.: Analytica posteriora; see Aristotle.

Aristotle, The Works of Aristotle translated into English, ed. W.D. Ross, Oxford: Clarendon Press 1912-52.

Bonaventure, Opera theologica selecta, Quarrachi: Collegium S. Bonaventurae 1934-.

Dial.: See William of Ockham, Dialogus.

EN: Ethica Nicomachea; see Aristotle.

Gratian: see Friedberg.

Friedberg, Aemilius, Corpus iuris canonici, Leipzig: Tauchnitz 1879.

Gregory of Rimini, Lectura super primum et secundum sententiarum, ed. A. Damasus Trapp, et al., Berlin: De Gruyter 1980.

Long, A.A., and D.N. Sedley, The Hellenistic Philosophers, Cambridge: Cambridge University Press 1987.

OTh: See William of Ockham, Opera theologica.

Pol.: Politica; see Aristotle.

Raphael, D.D. (ed.), British Moralists 1650-1800, Oxford: Clarendon Press 1969.

Rhet.: Rhetorica; see Aristotle.

Rufinus, Summa decretorum, ed. H.Singer, Aalen: Scientia-Verlag, 1963, Reprint of the 1902 edn.

Scotus, Ioannes Duns, Opera omnia, ed. C. Balić et al., vol. 6, Rome: Typis Polyglottis Vaticanis, 1963.

Suarez, Francisco, De legibus, ed. L. Pereña et al., Madrid: Consejo Superior de Investigaciones Cientificas, Instituto Francisco de Vitoria 1971.

William of Ockham, Opera theologica, St. Bonaventure, N.Y. : Franciscan Institute 1974-1984.

William of Ockham, Dialogus: Latin Text and English Translation, ed. J. Kilcullen, J. Scott, G. Knysh, V. Leppin, and J. Ballweg, London: British Academy, http://www.britac.ac.uk/pubs/dialogus/ockDial.html.

Wolter, A.B. (ed. and tr.), Duns Scotus on the Will and Morality, Washington: Catholic University Of America Press 1986.

 

Secondary sources:

Buckland, W. W., 1975, A Text-Book of Roman Law, 3rd edn., revised by Peter Stein, Cambridge: Cambridge University Press.

Buckle, S., 1991a, Natural Law and the Theory of Property: Grotius to Hume, Oxford: Clarendon Press.

Buckle, S. 1991b, “Natural Law”, in Peter Singer (ed.), A Companion to Ethics, Oxford: Blackwell (1991), 161-74.

Chroust, A.-H., 1943, “Hugo Grotius and the Scholastic Natural Law Tradition”, New Scholasticism, 17: 101–133.

Chroust, A.-H., 1944, “The philosophy of law of St Augustine”, The Philosophical Review, 53: 195-202.

Crowe, M.B., 1977, The Changing Profile of the Natural Law, The Hague: Martinus Nijhoff.

Cunningham, S. B., 1967, “Albertus Magnus on Natural Law”, Journal of the History of Ideas, 28: 479-502.

de Romilly, J., 1992, The Great Sophists in Periclean Athens, tr. Janet Lloyd, Oxford: Clarendon Press.

Eschmann, I. T., 1943, “A Thomistic Glossary on the Principle of the Preeminence of a Common Good.” Medieval Studies 5: 123–65.

Eschmann, I. T., 1944, “Bonum Commune Melius Est Quam Bonum Unius. Eine Studie über den Wertvorrang des Personalen bei Thomas von Aquin”, Medieval Studies 6: 62–120.

Eschmann, I. T., 1946, 1947, “Studies on the Notion of Society in St. Thomas Aquinas”, Medieval Studies 8: 1–42; 9: 19–55.

Finnis, J., 1980, Natural Law and Natural Rights, Oxford: Clarendon Press.

Finnis, J., (ed.), 1991, Natural Law, Aldershot: Dartmouth.

Grisez, G., 1965, “The First Principle of Practical Reason: A Commentary on the Summa theolgiae, 1-2, Question 94, Article 2”, Natural Law Forum 10: 168-201, reprinted in Finnis 1991, 191-224.

Haakonssen, K., 1992, “Natural Law Theory”, in Lawrence C. Becker and Charlotte B. Becker, eds. Encyclopedia of Ethics, New York: Garland.

Kilcullen, J., and Scott, J., (trans.), 2001, William of Ockham, Work of Ninety Days, Lewiston: Edwin Mellen Press.

Kilcullen, J., 2001a, “Natural Law and Will in Ockham”, in Kilcullen and Scott, 2001, 851-882, wwill.html

Kilcullen, J. 2001b, “The Origin of Property: Ockham, Grotius, Pufendorf and Some Others”, in Kilcullen and Scott, 2001, 883-932, wprop.html

Kölmel, Wilhelm, 1953, “Das Naturrecht bei Wilhelm Ockham”, Franziskanische Studien 35: 39-85.

Mäkinen, V. and P. Korkman (eds.), 2006, Transformations in Medieval and Early-Modern Rights Discourse, The Netherlands: Springer.

McGrade, A.S., 1999 “Natural Law and Moral Omnipotence”, in P.V. Spade (ed.), The Cambridge Companion to Ockham, Cambridge: Cambridge University Press, 273-301.

McGrade, A.S., 2006, “Right(s) in Ockham: A Reasonable Vision of Politics”, in Mäkinen, 63-94.

Mill, J.S., 1963, Collected Works, ed. J. Robson et al., Toronto: University of Toronto Press.

Murphy, M., 2008, “The Natural Law Tradition in Ethics”, The Stanford Encyclopedia of Philosophy (Spring 2008 Edition), Edward N. Zalta (ed.), http://plato.stanford.edu/archives/spr2008/entries/natural-law-ethics.

Quinn, J. F., 1974, “St Bonaventure’s Fundamental Conception of Natural Law”, in S. Bonaventura 1274-1974, Grottaferrata: Collegio San Bonaventura, 3: 571-98.

Ragland, C.P., 1998, “Scotus on the Decalogue: What Sort of Voluntarism?”, Vivarium 36: 67-81.

St. Leger, J., 1962, The “Etiamsi Daremus” of Hugo Grotius: A Study in the Origins of International Law, Rome: Pontificium Athenaeum Internationale.

Tierney, B., 1997, The idea of natural rights : studies on natural rights, natural law and church law 1150-1625, Atlanta: Scholars Press.

Tierney, B., 2001, “Permissive Natural Law and Property: Gratian to Kant”, Journal of the History of Ideas 62: 381-99.

Tierney, B., 2002, “Natural Law and Natural Rights: Old Problems and Recent Approaches”, Review of Politics 64: 389-410.

Williams, T., 1997, “Reason, Morality and Voluntarism in Duns Scotus: A Pseudo-Problem Dissolved”, The Modern Schoolman 74: 73-94.

Zuckert, M., 1997, “Do Natural Rights Derive From Natural Law?” Harvard Journal of Law and Public Policy 3: 695-731.

Zuckert, M., 2007, “The Fullness of Being: Thomas Aquinas and the Modern Critique of Natural Law”, Review of Politics 69: 28-47.


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