Natural Law Change by Addition,Original Sin and Ius Gentium: Toward a New Interpretation of Thomas Aquinas's Theory of Property (Part I)

Property in the State of Innocence

In ST II-II, q. 66, a. 1, Thomas asks whether it is natural for man to possess external goods. He is not referring here to the private possession/ownership of goods, ⁴⁰ but rather to the appropriation of external things by the rational creature for his usefulness. At first glance, the question may seem idle. After all, without this use, human survival would simply be impossible. But this only shows that the possession of external goods is natural to human beings. As usual, Aquinas presents philosophical and theological justifications to support his point of view (both, obviously, always convergent). Philosophically, he relies on Aristotle (I Polit.), arguing that man, being endowed with reason and will, is the most perfect among material creatures, and ‘things that are less perfect or less complete (imperfectiora) exist for the sake of things that are more perfect or more complete (perfectioria)’. ⁴¹ Theologically, his argument is based on the book of Genesis: ‘Now this natural dominion over other creatures that belongs to man in accord with his reason, in which the image of God consists, is made manifest in the very creation of man in Genesis 1:26, where it says: “Let us make man to our likeness and image and set him above the fish of the sea, etc.”’ ⁴²

This first consideration about property is, therefore, generic. Possessing external goods is natural to human beings (possessio rerum exteriorum est homini naturalis), exercised through man's participation in God's dominion over all things, by having been created imago Dei. ⁴³ This natural right is the foundation of one of the most important principles of Catholic social teaching, namely, the principle of the universal destination of goods. It is not a mere coincidence that Thomas commences his reflection on property, in the first article of question 66, by addressing precisely this principle. The institution of private property, which will be examined in ST II-II, q. 66, a. 2, is subordinate to the principle of the universal destination of goods and cannot derogate from it.

After establishing that the possession of external goods is natural to man, Aquinas goes on to discuss, in ST II-II, q. 66, a. 2, the forms that such possession can assume, and its connection with natural law. This is where he investigates whether it is licit to possess a thing as one's own (utrum licitum sit quod aliquis rem aliquam possideat quasi propriam). In response to the first objection, Thomas affirms that

Community of goods is ascribed to the natural right (iuri naturali), not because the natural right dictates that all things are to be possessed in common and that nothing is to be possessed as one's own, but because the division of possessions itself is not a matter of the natural right, but rather a matter of human agreement, which, as was explained above (q. 57, aa. 2–3), pertains to the positive right. Hence, the ownership of possessions is not contrary to the natural right but is added to the natural right by the advent of human reason (sed iuri naturali superadditur per adinventionem rationis humanae). ⁴⁴

If Aquinas limited himself to asserting that the divine right to the community of goods does not pose an obstacle to the implementation of the division of possessions by human laws, he would not be affirming anything substantively different from what Augustine had stated centuries earlier. ⁴⁵ In that case, the institution of private property would fall within the realm of purely conventional right, which means that, as Richard J. Dougherty aptly noted, the rightful claim to private property would always be circumscribed by the human positive law and, thus, when contested, would have to be adjudicated by the civil authority: ‘That is to say, individual or private rights are not understood as “natural” rights, for they do not inhere in individuals absent their recognition by the law.’ ⁴⁶ But this is not Thomas's position. The Angelic Doctor takes a step further in relation to Augustine by establishing that the ownership of possessions is an addition to the natural law made by the advent of human reason, thus envisioning a connection between the institution of private property and the natural law that had not been envisaged by any of his predecessors. This, as we will see, makes all the difference.

The comparison between the human condition before and after the fall is crucial to accurately understand Thomas's view on property. There are two factors that, essentially, must be considered in this comparison: (i) the deprivation of the original state of Justice and (ii) the problem of the scarcity of goods.

In several passages of the Treatise on Man, Aquinas says that, in the state of innocence, passions were totally submitted to reason. ⁴⁷ It is the opposite of what occurs in the present state, in which our passions ignite at the slightest spark and easily become disordered. With the fall, we also began to be governed by the law of the fomes of sin (lex fomitis [peccati]), ⁴⁸ which, despite not being a law simpliciter, i.e., absolutely considered (as the eternal, divine, natural and human laws are), participates, albeit peculiarly, in the eternal law, that is, in the form of punishment imposed by God on humanity due to original sin. Thomas considers it ‘law’ in a very particular aspect (secundum quid), which is that it brings to light the numbness of reason resulting from the fall.

The main consequence of reason completely controlling the passions is that, in the state of perfect nature, human beings could fulfill all precepts of the law without the need for help from grace, at least regarding the substance of the works. ‘But in the state of corrupted nature man cannot fulfill all the Divine commandments without healing grace.’ ⁴⁹ However, as for the mode of acting, i.e., their being done out of charity, ‘neither in the state of perfect nature, nor in the state of corrupt nature can man fulfill the commandments of the law without Grace’. ⁵⁰

The scarcity of goods is another determining factor in this discussion. In the state of perfect nature there was no scarcity, as human beings ‘would not have had any bodily need of animals—neither for clothing, since then they were naked and not ashamed, there being no inordinate motions of concupiscence—nor for food, since they fed on the trees of paradise’. ⁵¹

The absolute control of reason over passions and the abundance of goods, enough to satisfy human beings to the extent of their needs, sufficiently explains why, before the fall, the commonality of goods was a natural right. These two factors are unequivocally summarised in the passages that will be examined below.

The third objection raised in ST I, q. 98, a. 1—an article in which Aquinas discusses whether there would be generation before the fall—raises the following problem: by generation human beings are multiplied, and the multiplication of the human race requires the division of goods, to avoid confusion of dominion (confusionem dominii ⁵² ). But this, the objection goes on, is against natural law, according to which all things are held in common.

In our present state, it is necessary for there to be a division of possessions when those who have dominion multiply. For as the Philosopher says in Politics 2, the holding of possessions in common (communitas possessionis) is an occasion for discord. However, in the state of innocence, men's wills were ordered in such a way that, without any danger of strife, they would have had, to the extent appropriate for each, common use (communiter usi fuissent) of the goods that fell under their dominium. For this practice is observed even now among many good men. ⁵³

Most of Thomas’s reflections in the Treatise on Man concern the perspective of what our life would have been like in Paradise if original sin had not been committed. Taking into account our privileged bodily and intellectual conditions before the fall, Aquinas speculates, for instance, about how we would preserve our being (I, q. 97); how the human species would be conserved (I, q. 98); the condition of the offspring to be generated, regarding body, justice and knowledge (I, qq. 99–101); and what the political community would be like (I, q. 96, a. 4). The latter is developed from the perspective of two meanings that can be assigned to the word ‘dominion’. The first is in a sense of opposition to servitude (servituti): ‘In this sense, a lord (dominus) is one to whom someone is subject as a servant (servus).’ ⁵⁴ The second refers to the role of governing and directing other free people (officium gubernandi). Thus, Aquinas concludes that, in the state of innocence, in the first sense, one man would not dominate over another; but in the second, he could dominate. In other words: before the fall, there would be political community, but there could not be servitude, and private property would not have been necessary. ⁵⁵

Property and the Psychology of Fallen Man

With the fall, the scenario changes radically. As punishment for original sin, submission of passions to reason began to require great effort, in addition to the assistance of Grace. From this condition arises the law of sin (lex fomitis), which consists in the rational perception of the constant difficulty of conforming, in the words of Saint Paul, ⁵⁶ the law of our members to the law of our mind. All of this, combined with the scarcity of goods, made the institution of private property a necessity, so that the management of goods in the present state would be more efficient, more ordered, and more peaceful in the political community. Socialist experiments confirmed the views of Aristotle and Thomas Aquinas. Attempts to abolish private property led, precisely, to glaring inefficiency in the management of goods, generating misery on a large scale, widespread disorder, and serious social conflicts.

The reasons that justify the institution of private property in the state of corrupted nature are listed in ST II-II, q. 66, a. 2, resp. Thomas says there are two attributions related to this right: (i) the power to take care of and manage exterior things (potestas procurandi et dispensandi), and (ii) the use of them. Aquinas extracts from the first attribution three arguments in favour of possessing external goods as one's own: it brings more order and peace to the community, in addition to providing more efficient management of goods. ⁵⁷

Regarding use, Thomas says that ‘man should hold his exterior things not as his own but as common, in order that he might freely share them when others are in need (de facili aliquis ea communicet in necessitate aliorum)’. ⁵⁸ He is firmly anchored in Aristotle, who, in Politics (Book II), maintains that, although property should be private, its use should be common. ⁵⁹ As Casanova observed, ⁶⁰ Aquinas connects this idea with a quote from The First Epistle of St. Paul to Timothy (6:17–19), in which the Apostle exhorts the rich ‘to be generous and willing to share’. Hence, for Thomas, ‘common use’ has the meaning of a moral obligation. ⁶¹ This obligation, however, does not give those who are in a state of poverty the right to snatch such goods, except in cases of extreme necessity (as we will see later).

Interestingly, despite the need to establish the institution of private property as a result of the consequences of original sin, the commonality of things remained, for Thomas, a natural right. At this point, Aquinas is closely following Isidore of Seville and, through it, the entire patristic tradition. Furthermore, when theorising about the division of goods, Thomas never strays far from the biblical narrative. Our natural inclinations have not been changed by the fall. ‘For what is natural to man is neither taken away from nor added to man because of sin.’ ⁶² It means that, since human beings did not have a natural inclination to possess external goods as their own before the fall, they could not have acquired it in the present state, as original sin did not add new inclinations to them, nor did it subtract those they already had. ⁶³ Private property arose, therefore, not as a new primary precept of natural law, but as something useful to human life, which was introduced by the advent of human reason (per adinventionem rationis humanae). ⁶⁴

For this paper, ST II-II, q. 66, a. 7, is most directly relevant. In it, Aquinas investigates whether it is lawful to steal out of necessity. In accordance with the natural order, established by Divine Providence, inferior things are ordered to alleviate human needs. Thomas refers here to the principle of the universal destination of goods, gleaned from the Gospels and the teachings of the Church Fathers. Thus, for Aquinas, the institution of private property through positive law cannot generate a situation of inequity such that it prevents the satisfaction of the most basic needs of human beings. Therefore, things which we possess in superabundance are due by natural law to the support of the poor. That is, we have a moral obligation to give the poor the goods we have in abundance. ⁶⁵ However, this moral obligation, as a rule, does not give those who are in a state of poverty the right to take possession of other people's assets. If the needy person does so, he commits an injustice and therefore a sin—after all, theft, as contrary to charity, is a mortal sin. ⁶⁶

In this manner, when Aquinas says things that some individuals have in abundance are owed by the natural right to sustain the poor, but that, as a general rule, it is up to each person's discretion to dispense their own goods in order to provide relief to those in need, he is affirming that this is a moral obligation without legal repercussions. ⁶⁷ Or, in the terms put by Thomas himself: there is a moral debt (debitum morale), but not a legal debt (debitum legale). ⁶⁸ Although the conduct of the possessor of surplus goods who refuses to provide for those in need is not unlawful, as the legal order guarantees him private property, it is endowed, as is the case with all properly human acts, with moral relevance ⁶⁹ : the possessor is acting against natural law and therefore sinning, which is equivalent to offending God and neighbour. More precisely, he is committing the sin of avarice, which is directly ‘a sin against one's neighbor, since in the case of exterior riches one man cannot have a superabundance without another's falling short. For temporal goods cannot be possessed by many individuals at the same time.’ ⁷⁰

However, if the need is urgent (Aquinas is referring to extreme situations, involving danger of death), the person is authorised to relieve his necessity with things that are under someone else's property. The conservation of our own being is a moral obligation. Since the community of goods is a natural right, it follows that, in the case of urgent need, the convention that establishes private property must be set aside, since ‘things that fall under the human right cannot detract from the natural right or from the divine right’. ⁷¹ With the dissolution of the convention, the state of communal goods existing before the fall is restored, so that the person will neither commit theft nor robbery, ‘because of such a need the thing that one takes in order to sustain his own life becomes his own’. ⁷² Furthermore, since the appropriation of other people's property is ordinarily considered a crime, the positive human law, in this exceptional situation, must intervene to legitimise the conduct of the person in urgent need.

Without reference to what Aquinas says in the Treatise on Man, it is impossible to understand his vision about the commonality/division of goods. Thomas quotes a passage from The Etymologies, in which Isidore says that ‘the common possession of everything’ is a natural law. ⁷³ As we have seen, this was an opinion largely shared by the Church Fathers. This vision permeated the entire patristic period, which ended up with Isidore of Seville in the West and John Damascene in the East, reaching scholasticism and Thomas Aquinas. Thomas knew in depth the teachings of the Church Fathers, which he absorbed and considered when he reflected on the subject. That is to say: although Isidore is his direct and express source, it seems that both Isidore and Aquinas had the same influences.

Considering this, we understand why Aquinas does not hesitate to assert that the commonality of things is a natural right. In the Commentary on the Sentences, we find this statement: ‘Private property is not what is primarily intended by nature, according to which all things are common’ (Rerum appropriatio non est de prima intentione naturae, secundum quam omnia sunt communia). ⁷⁴ Some might affirm this is an isolated statement, made by a young Thomas. But it is not. The same idea would appear again in his most mature work, the Summa Theologiae, in other words: ‘The community of goods is ascribed to the natural law’ (communitas rerum attribuitur iuri naturali). ⁷⁵

There seems to be no doubt that Aquinas is trying to harmonise the Gospels ⁷⁶ and the opinions of the Church Fathers with the lessons of Aristotle. ⁷⁷ From the Gospels and the writings of the Church Fathers, it is unquestionable that exterior goods were held in common before the fall and would have continued to be held so if man had not fallen; ⁷⁸ it was, therefore, a natural right. Original sin did not change our natural inclinations—it did not bring us new inclinations nor take away any of those we already had. From this, it can be concluded that the commonality of things remains a natural right even after the fall. Nonetheless, in the present state, the division of possessions has become a necessity. ⁷⁹

It turns out that private property cannot be situated within the realm of purely conventional justice, since Aquinas considers it as an institution of the law of nations, which he understands to be a component of natural law. Therefore, the hypothesis that private property is a mere conventional right must also be discarded. This will become even more evident after examining three passages from the Summa Theologiae: II-II, q. 57, a. 3, resp.; I-II, q. 95, a. 4, resp.; and I-II, q. 94, a. 5. Their analysis will lead us to the third and fourth investigative hypotheses.

Aquinas's Interpretation of Gaius, Ulpian, and Isidore on Natural Law, Civil Law, and the Law of Nations

The sources expressly mentioned by Aquinas in ST II-II, q. 57, a. 3, are Gaius and Ulpian, through quotations from their writings incorporated in the Digest, and Isidore of Seville, the latter extracted from Decretum Gratiani. ⁸⁰ All these quotations concern the classification of law into natural law, civil law, and the law of nations, which are widely discussed by the scholastics. Thomas's aim is, more precisely, to investigate the relationship between the law of nations and natural law. Knowing these sources is crucial to understanding his conclusions.

According to Isidore, natural law is common to all nations and exists universally by the instinct of nature, without the need for regulation. Civil law is specific to each individual population or city, established for human or divine reasons. The law of nations is a set of principles used by nearly all nations.

Gaius, in turn, uses a bipartite classification of law—civil law and law of nations. His definition of ius gentium resembles the classical notion of natural law: ‘Among all men natural reason (ratio naturalis) puts in place what is preserved among all the nations, and this is called the right of nations.’ ⁸¹ However, in the passage cited, the expression ius naturale does not appear, but rather ratio naturalis. According to Wauters, many glossators endorsed Gaius’s idea that the ius naturale was connected to the ius gentium via ratio naturalis. ⁸²

Ulpian was the one who used the expression ‘ius naturale’, but in a sense that, at first glance, does not seem to be the same as that used by classical natural law theorists:

Jus naturale is that which nature has taught to all animals; for it is not a law specific to mankind but is common to all animals—land animals, sea animals, and the birds as well. Out of this comes the union of man and woman which we call marriage, and the procreation of children, and their rearing. So we can see that the other animals, wild beasts included, are rightly understood to be acquainted with this law. ⁸³

In the face of the distinct classifications of Ulpian, Gaius, and Isidore, Thomas considers it pertinent to ask whether the ius naturale is the same as the ius gentium.

Firstly, we should analyse how Aquinas interprets Ulpian's concept of natural right. It is noted that Ulpian refers to natural right as something converging with biological laws, which leads him to conclude that such right ‘is common to all animals’. ⁸⁴ This view seems quite different from the classical one, in accordance with which the law is something pertinent to reason. ⁸⁵ It is a fact that brute animals, as well as all created beings, receive their inclinations from the eternal law, which directs them to their proper end. This participation is said to be passive. It turns out that the rational creature, in addition to passively participating in the eternal law, also participates in it intellectually, which gives him an active position in Divine Providence. ⁸⁶

If one examines Ulpian's definition based on the sophisticated theoretical equipment developed by Aquinas, one gets the impression that the jurisconsult is promoting a confusion of registers, perhaps an undue transposition between genres (metábasis eis állos genus), by extending the application of natural right to non-rational animals. As all created beings do, human beings passively participate in the eternal law. For creatures inferior to man, however, this participation has the character of biological law, object of study of biology, and not of a natural law or natural right, object of study of ethics and metaphysics, ⁸⁷ unless in a qualified and analogical sense. That is to say: what for Aquinas is natural law by way of similitude (per similitudinem), Ulpian takes to be the natural law in the absolute sense (proprie lex vocatur). ⁸⁸ Yet, things are somewhat more complex than this.

The interpretation of Ulpian regarding the notion of ius naturale, and mostly its reception by Thomas, cannot be properly understood without reference to the doctrine that ‘art imitates nature’ (ars imitatur naturam), which permeates Aquinas's moral thought. In his extensive and sharp study on the subject, Golubiewski highlights this important point of Thomas's thinking, which has been systematically ignored by most of the contemporary natural law theorists. ⁸⁹ When Aquinas states that ‘art imitates nature’ (‘art’ in a broad sense, encompassing the sphere of human action ⁹⁰ ), he obviously does not mean, as Stephen L. Brock says, ‘a slavish sort of imitation, sheer mimicry. The moral order is not a copy of the natural. They are analogous. They have common, sapiential principles. And the natural order must come first, both in reality and in knowledge.’ ⁹¹ Golubiewski writes:

Why then in his moral doctrine does he seem to draw on the considerations that belong to other orders of knowledge? Does he perhaps ignore differences between natural philosophy and moral reasoning? No, he does not. He is aware that unlike natural philosophy and metaphysics, moral thinking not only considers but also makes an order. Rather, his moral teaching is based on the analogical principles of good agency manifest in different natural agents and their congruent operations, including those that are the object of natural philosophy. In the doctrine of the imitation of nature by reason, virtue, and grace, Aquinas connects the intelligible principles of good agency of different natural agents and their respective natural movements with the order of human moral agency. Imitation of nature is therefore for Aquinas the source of intelligibility of practical reasoning and of the morally virtuous character of the human agent. In light of his teaching, the imitation of nature not only provides answers about how we apprehend practical principles, or more precisely their terms, but also unveils the natural source of intelligibility of morally good and virtuous agency. His doctrine of the imitation of nature shows that right moral reasoning is deeply rooted in and in harmony with the universal symphony of sensible natures. In light of this doctrine, to act morally well is naturally good for human agents, just as for other natural things it is naturally good to operate as their respective natures determine. ⁹²

This doctrine is on a collision course with the theses advocated by the so-called ‘New Natural Law Theory’. It is not my aim to delve deeper into the debate regarding the theories of Finnis and Grisez in this essay. However, it must be emphasised that the notion of ius naturale proposed by Ulpian, and especially its absorption by Thomas Aquinas, simply cannot be consistently explained by the Grisez-Finnis system, given that these authors understand that practical reason is autonomous, i.e., it does not depend on any prior speculative knowledge of nature, including human nature. According to Finnis himself, the first principles of practical reason ‘make no reference at all to human nature, but only to human good’. ⁹⁵ It so happens that, contrary to what Finnis and Grisez maintain, for Aquinas, speculative knowledge not only of human nature but of nature as a whole has ethical relevance, as it expresses the wisdom of God embodied participatively in His creation, a wisdom that human beings know speculatively and apprehend imitatively. Thomas is crystal clear on this point: ‘Since those things that are in accord with nature are ordered by God's reason, which human reason ought to imitate, anything done by human reason which is contrary to the order commonly found among natural things is defective and a sin (est vitiosum et peccatum).’ ⁹⁶ Natural agents and their congruent operations, including those that are the object of natural philosophy, provide a kind of metaethical substrate for human intellect, nourishing it with sapiential and universal principles that forge the more specific principles of practical reason, derived from an anthropological-metaphysical understanding of human nature. Aquinas, of course, was aware of the immense differences between rational and non-rational creatures, which is why, for him, the application of these principles in the sphere of morals will always be analogical.

All this considered, it is not surprising that Thomas does not dismiss Ulpian's conceptualisation, but rather strives to give it some usefulness in the context of the problem he is investigating. ⁹⁷ Aquinas begins his response by saying that ‘natural right or justice is what, by nature, is adequate and proportionate to something else’ (ius sive iustum naturale est quod ex sui natura est adaequatum vel commensuratum alteri). ⁹⁸ In continuation, he explains that this adequacy or commensurability can occur in two modes: (i) by virtue of an absolute consideration (secundum absolutem sui consideratione), in the way that a male is by his very nature commensurated to a female in order that he might generate from her, and in the way that a parent is commensurated to her child in order that she might feed him; (ii) not out of absolute consideration, but with respect to the consequences resulting from nature (secundum aliquid quod ex ipso consequitur). ⁹⁹

From the examples related to the first mode, which adopts the criterion that I will name ‘the absolute adequacy of good to nature’, we can rapidly verify that Aquinas is referring to the three levels of natural inclinations. ¹⁰⁰ From this it follows that all these inclinations lead to goods that are absolutely adequate or proportionate to the natures to which they refer. Therefore, they belong to natural law by virtue of an absolute consideration (secundum absolutem sui consideratione). It seems that here Thomas is modifying the key of his definition, formulating an extended concept of natural law that places emphasis not on the active participation of the moral agent in the eternal law, but on the commensurability of certain goods to animals, which results, as with everything in the order of creation, from passive participation in the divine intelligence. Now, according to this broad sense (by virtue of an absolute consideration), it can be said that both rational and non-rational creatures are governed by a ‘natural right’, given that they have the first and the second orders of inclinations in common, to which correspond goods that are absolutely appropriate or proportionate to them (the conservation of being, the union between male and female, the procreation and education of offspring, etc.). Obviously, in the case of human beings, this absolute adequacy is apprehended rationally, through active participation in the eternal law, which, backed by passive participation, gives rise to natural law in the absolute sense. However, in the case of non-rational animals, such adequacy, despite being processed by virtue of an absolute consideration, can only be named ‘natural law’ by similarity. By allowing Ulpian's definition to be encompassed by a broader concept of natural law, Aquinas saves it from the fallacy of undue transposition between genres, giving it sufficient theoretical dignity so that it can be compared with the definitions of natural law and the law of nations proposed by Gaius and Isidore.

But what about the second mode? What does it mean to say that one thing is adequate to another with respect to the consequences resulting from nature (secundum aliquid quod ex ipso consequitur)? Thomas refers to the consequences of something being one way or another, whose convenience only reason can ponder. ¹⁰¹ The example that Aquinas provides in this second mode is precisely the institution of private property (proprietas possessionum), which, at the end of the response, he relates to the ius gentium.

For instance, if a field is considered absolutely, then there is no reason why it should belong to this individual rather than to that one; however, as is clear from the Philosopher in Politics 2, if the field is considered with respect to the opportunity to cultivate it and use it peaceably, then it is commensurated to belonging to the one individual rather than the other. ¹⁰²

At ST II-II, q. 57, a. 3, we find clear evidence that, in Thomas's theory of property, the possession of exterior things as one's own is not a natural human inclination. If it were, Aquinas would associate it with the natural law by virtue of absolute consideration. There was the possibility that he considered private property as pertaining to natural law in terms of this first mode—a good that would flow directly from a natural inclination of human beings to possess external goods as their own implicit in the third order of inclinations. But Thomas rejects this hypothesis: he considers private property a natural right according to the criterion of the consequential adequacy of the good to nature. And he does so due to an imperative of coherence: as we had no natural inclination to possess external goods as our own in the state of innocence, we could not have acquired it in the present state.

The natural human inclinations, from which are derived goods that are absolutely proportionate to man, have accompanied him unchanged since creation. They are a direct result of the divine will and rationality manifested in man created imago Dei. For this very reason, natural law is the participation of eternal law in rational creatures, which we know through the natural inclinations that were impressed on us by the Creator. ¹⁰³ But the possession of external goods as one's own is not a natural inclination. Private property is an institution of positive law that, at the same time, has a certain type of connection with natural law. This connection is not absolute, but rather relative and consequential—an addition made to natural law by the advent of human reason, for the usefulness of human beings.

This considered, it seems that the precepts of natural law by virtue of an absolute consideration (secundum absolutem sui consideratione) and the precepts which pertain to the natural law according to the criterion of the consequential adequacy of the good to nature (secundum aliquid quod ex ipso consequitur) do not participate in the eternal law in the same way. I will argue that the ponderation on the mode of participation of this second category of precepts, to which the institution of private property belongs, must take into account the law of sin, although, I emphasise, the division of possessions is not a punishment for original sin, but a psychological consequence of this punishment.

Private Property and the Law of Sin (Lex Fomitis)

When dealing with the law of sin, ¹⁰⁴ Aquinas argues that, for human beings, in a proper or absolute sense, the law is something pertinent to reason, and that such a law was so effective in the primitive state that nothing either beside or against reason could take human beings unaware. But when we turned our back on God, we fell under the influence of our sensual impulses. Such impulses, for non-rational animals, simply have the nature of a law (being fierce is in a certain sense the law for a dog, whereas it is contrary to the law for a sheep or some other gentle animal). For human beings, the law of sin can solely be considered law secundum quid, concerning our (rational) perception that, due to the fall, we were punished with the deprivation of original Justice. ¹⁰⁵

The natural law can be observed in the natural inclinations imprinted upon human beings by God in the very first act of creation, from which flow goods that are absolutely proportionate to them. From these inclinations can be extracted the precepts of natural law (primary, secondary and tertiary), which are endowed with intrinsic and absolute goodness. Knowing them, we participatively know the will and reason present in the mind of God, who wanted and made them so because they are good in themselves: ‘For in divine law certain things are commanded because they are good and prohibited because they are bad, whereas there are other things that are good because they are commanded and bad because they are prohibited.’ ¹⁰⁶ This explains why the natural law is the eternal law present in the rational creature within the limits of his finitude. ¹⁰⁷

But possessing external goods as one's own is not and could not be a natural human inclination, given that, in the order of creation, both the division and the commonality of things were and continue to be adopted—it is Aquinas himself who says that the latter was observed in his time among numerous good people (and so goes on today).

Original sin is, undoubtedly, the turning point in our analysis. Before the fall, the commonality of goods was convenient because human beings, invested with original Justice, had their wills ordered in such a way as to enable them to hold things subject to their dominion in common without danger of strife. In another turn, after the fall, the consideration of which property regime should be adopted needs to take into account the penalty of deprivation of original Justice imposed upon humanity for original sin. Now, it can no longer be said that human reason apprehends the divine will and reason participated in the natural human inclinations. Under the warning of the law of sin, human reason recognises the psychological necessity in adopting, in the present state, the division of possessions, adding a new right to the natural law. This, however, in no way interferes with human beings’ natural inclinations, given that the institution of private property does not have the character of an end, but rather of a means—an instrument to facilitate the pursuit of human goods and the ultimate end of man, the beatific vision.

In ST II-II, q. 66, a. 2, ad 1, Aquinas emphasises that the connection between the institution of private property and the natural law occurs (i) in the manner of addition and (ii) through the advent of human reason (sed iuri naturali superadditur per adinventionem rationis humanae). The same idea appears in I-II, q. 94, a. 5, resp., where he says that many things were added to the natural law by human laws, useful for human being's lives. By emphasising that this second mode through which something is attributed to natural law comes from human reason, Aquinas seems to have the intention of differentiating it from the other mode in which the natural law arises directly from divine reason (rationis divinae). This is exactly what happens with the precepts belonging to natural law by virtue of an absolute consideration (secundum absolutem sui consideratione): when contemplating natural inclinations and the goods that are absolutely appropriate to them, we know the divine reason itself participated in human nature.

Regarding the precepts which pertain to natural law according to the criterion of the consequential adequacy of the good to nature (secundum aliquid quod ex ipso consequitur), human reason considers the convenience of adopting certain institutions or means capable of making the achievement of human beings’ natural ends and their finis ultimus more conducive, taking into account the consequences of its implementation. Aquinas is clear in asserting that, in this second case, the precepts of natural law arise by the advent of human reason. It is as if natural law had, in the mode of absolute consideration, its direct source in the eternal law, and, in the mode of consequential consideration, in human reason, the eternal law being an indirect source, intermediated by the law of sin and the divine law. ¹⁰⁸

Given that original sin is a watershed, the analysis of how the law of sin impacts these two modes is essential. In any case, the law of sin has the role of alerting us to the numbness of our reason and the difficulties this brings to us in complying with the precepts of the law in the state of corrupt nature. The consequences of this warning, however, are quite different in each of these modes: (i) In the first, there is no modification of the natural law, ‘for what is natural to man is neither taken away from nor added to man because of sin’. ¹⁰⁹ Such an alert warns the rational creature of the need for Grace's assistance to fulfil the precepts of the law (both with respect to the substance of the deeds and the mode of acting—with charity ¹¹⁰ ) and the divine law's help to guide him straight towards his ultimate end. ¹¹¹ (ii) In the second mode, under the admonition of the law of sin, human reason supplements natural law with rights, seeking to make the flourishing of our natural inclinations more attainable, while also accounting for the fragile condition of our rationality in the present state. These additions do not have the character of ends, but of means, which human reason, after considering the consequences of their implementation, deems convenient.

In the second part of this article, I will proceed with a more thorough analysis of this third investigative hypothesis. The inquiry will focus on a detailed exploration of the moral and legal status of the law of nations, as well as its relationship to the institution of private property. Subsequently, I will advance to a discussion of the fourth and final investigative hypothesis. I aim to conclude by demonstrating how Thomas Aquinas's theory of property underpins the principles enshrined in the social doctrine of the Church.