- 1 An analysis of the way in which the Aristotelian philosophical framework or the biblical and theolo (...)
1In a landmark article published nearly sixty years ago, Lynn White (1967) predicted the ecological disaster that was likely to come. In particular, he supposed, the medieval conception of man and nature, being steeped in Christian anthropocentrism, was at the root of productivist industrial development and the consequent environmental devastation (White, 1967). White’s critique takes on a new relevance today, at a time when the ecological question and its link with economic activity is becoming ever more pressing; hence it is appropriate to examine medieval economic thought in order to identify what it may have carried in terms of the seeds of disaster, or, on the contrary, what in it might resonate with contemporary ecological problems. To carry out this investigation, I focus on the economic writings of Thomas Aquinas (c. 1225-1274). This means that I adopt a triple restriction, limiting my investigation (1) to one author, although one of the most important of this time, (2) to his economic texts in particular, and (3) to a reading based on economic analysis.1
- 2 For a recent review of this literature, see e.g. Januard (2025b, 28 and 39).
2Moreover, whereas the literature has mainly highlighted the insights of the Thomasian contribution on the issues of just price or usury,2 Aquinas offers an overview of economic activity, ranging from the reception of what the land produces to the satisfaction of needs through the work of the peasant, the craftsman, the merchant and through the justice of exchange. This overview is little known, probably because it is presented in a dispersed order and scattered throughout his works.
- 3 The term ‘ecology’, built on the Greek οἶκος (oîkos), ‘house, habitat’, and λόγος (lógos), ‘discour (...)
3The preoccupation that drives Aquinas is not ecology in the broad sense of preserving the natural environment, and in the context of the Middle Ages the term is anachronistic. I will show, however, that the whole process that he describes in a scattered way could indeed appear today as ‘ecological’ in the original sense of the term (Haeckel, 1866, 286), according to a reader-side hermeneutic, since Aquinas was of course unaware of either the lexicon or the concept.3 A multitude of more recent definitions could have been adopted; for the purposes of this article, it seemed that referring to the earliest known definition of ecology would be the least arbitrary choice. Since, according to this definition, ecology concerns “the relations of the organism with the surrounding external world” (Haeckel, 1866, 286). I take up the positive aspect of this definition to draw out a more normative meaning, which is in line with the current contemporary meaning, by considering the ‘ecological’ to be what allows this relationship to unfold in a harmonious and respectful way for the organism and its environment. I will show that this is translated, in the economic thought of Aquinas, into a respect for the organism through the satisfaction of its needs and a respect for its social and biological environment through the sobriety of its activity and the primacy assigned as a matter of principle to what the earth provides.
4Although this is a field that has not yet been explored in the literature, particularly with regard to Aquinas’s treatment of natural resources in relation to economic activity, or the unity of the process of production and the satisfaction of needs, I rely on several contributions that have highlighted the presence in Aquinas’s thought of a certain moderation in the different aspects of economic activity, whether production, trade, consumption, or gain (Langholm, 1992, 208-209; Franks, 2009, 99-104; Hirschfeld, 2018, 142-143; Koehler, 2020, 362; Santori, 2021, 29-21; or Alfani, 2023, 214-218). In addition, I take into account recent research which has shown that the notion of resource does not appear until well after the Middle Ages—I therefore use the contemporary expression ‘natural resources’ to describe what appears to us today as such, but without anachronistically affecting the perception of it to Aquinas—and that medieval human being does not situate himself in front of his environment but within a continuum (Arnoux, 2023).
5Although Aquinas stands out from contemporary issues by the absence of a thought of an extrinsic limit, two main characteristics of the Thomasian contribution may be identified, that can feed to contemporary reflection: the sobriety of economic activity and a unified process of satisfying need that starts by welcoming the earth’s gifts. I will deal with these in turn.
- 4 On loans at interest, see for instance, in the twelfth century, Gratian, Decretum, I, d. 46, c. 9–1 (...)
6On the one hand, there is a sobriety of economic activity (Section 1), which can be broken down in three ways. First, this activity is centred on exchange: indeed, the focus on exchange is a striking feature of medieval economic thought, whether it takes the form of interest-bearing loan or, to a lesser extent, commercial activity.4 Aquinas was part of this trend. Initially treated in dispersed order, commercial activity and lending are unified in the Summa theologiae under the notion of “voluntary exchanges” (S. T., IIa IIae, q. 77, Prol.). The goal of exchange is the satisfaction of needs. These needs are thought of by Aquinas as necessary, without superfluity, and therefore limited in their extension. Then, in order for exchange to occur and needs to be met, Aquinas considers the gain of the merchant or the different professions, but this gain must be moderate. Finally, Aquinas presents the two possible sources of supply and expresses his preference for local supply, albeit without neglecting the need for trade. He thus promoted trade in the form of short supply chains, which made supply more secure and avoided the inconveniences represented by the arrival of foreign merchants. As criteria of necessity in the definition of needs, moderation of gain and local supply lead to the consideration of a sobriety of economic activity which is not the result of an external limitation but of internal moderation.
7On the other hand, there is a unity and coherence in the process of the satisfaction of needs, understood as spanning from the earth’s production to the justice of exchange (Section 2). The production provided by the land constitutes the first step of this process, and is the principle that guides it. Whereas in some uses of the verb producere Aquinas does attribute an active role to human beings, in the only properly economic occurrence within a directly economic text Aquinas conforms to the biblical tradition of the Vulgate, which attributes production to the natural elements. In fact, in the economic passage of De regno, II, 7 (II, 3), it is the region which plays an active role, which produces and to which the wealth belongs, and which can be fertile and rich. Indeed, it was not until the seventeenth century that the lexicon of production took on its modern economic meaning. The primary role of the human being, then, is to choose where to establish the city according to the fertility of the land, and then to carry out the successive economic operations. It appears, in all the texts of Aquinas, that the role of reception and transformation by peasants and craftsmen, and then of transport and sale by merchants, is ordered towards exchange. Finally, the justice of exchange, particularly through the choice of the accurate kind of exchange ratio (price, stipend, …) and the notion of just price, ensures a good distribution and allows the satisfaction of needs. The justice of exchange is therefore not limited to protecting each of the stakeholders within a social relationship. It is invested with a much more fundamental mission, which is to ensure that the process of satisfying needs is achieved in accordance with its principle, namely what the land provides, and within the theological framework to which Aquinas adhered, namely what Divine Providence procures throughout the earth.
8The approach to economic activity that Aquinas proposes is based on the needs of the consumer and not on the gains of the producer or merchant. These needs are conceived in terms of goods necessary to life and not desire for goods that are optional or superfluous, which limits economic activity. Satisfying these needs requires a supply that will also furnish moderate gains, which are considered justified. While recognising the need for trade, Aquinas also emphasises the importance of short supply chains. The necessity of needs, the moderation of gains and the promotion of local supply lead to a global approach to activity characterised by sobriety, without deprivation or superfluity.
9In the Summa theologiae, Aquinas groups together under the heading of voluntary exchange some of the activities we would today call economic, namely commercial exchange and lending (S. T., IIa IIae, q. 77, prol.). His approach to activity is through exchange, the purpose of which is the satisfaction of needs, understood as finite natural needs, i.e. as elementary needs rather than constantly expanding needs (Hirschfeld, 2018, 64 and 139; Franks, 2009), and not as the endless pursuit of wealth, which constitutes avarice (Langholm, 1992, 208-210). The justice of exchange, through the notion of the just price, is based on this satisfaction of needs (Lapidus, 1994, 438-441).
10Aquinas states at the beginning of the economic part of the Summa theologiae that exchange takes place “for the common benefit of both parties [pro communi utilitate utriusque]”, since one “needs [indiget] what the other possesses” (S. T., IIa IIae, q. 77, a. 1, resp.). The lexicon of exchange is therefore that of utility and need. The introduction of the notion of utility (utilitas) could lead to a double misunderstanding. On the one hand, it is not understood in the contemporary sense of a utility function that would enable all quantities of goods and combinations of quantities of goods to be ordered. In its classical Latin and medieval sense, utilitas generally refers to the interest or advantage, in this case the interest or advantage of carrying out the exchange. Thus utilitas is opposed to detrimentum (detriment), as an operation can be to the advantage of one party and to the detriment of the other (S. T., IIa IIae, q. 77, a. 1, resp.), and to damnum (prejudice; S. T., IIa IIae, q. 78, a. 2, ad 1). Thus we are not here concerned with a material utility representing an order of preference between combinations of goods, but rather with an advantage that takes multiple forms, like those represented by human laws which do not repress all sins (S. T., IIa IIae, q. 78, a. 1, ad 3), those derived from friendship via the notion of “useful friendship” (S. T., IIa IIae, q. 77, a. 1, ad. 3; De malo, q. 13, a. 4, ad 5), or those derived from religious and spiritual life (De malo, q. 13, a. 4, ad 13 and 16). On the other hand, Aquinas does not consider a subjective utility or need specific to each individual agent and independent of the thing in itself. Things “have a certain utility from themselves [ex seipsis habent aliquam utilitatem]” (In III Sent., d. 37, a. 6, resp.). This explains the necessary reservation (Lapidus, 1986, 17-28; 1994, 440) about drawing from the medieval notion of utilitas the idea of a utility value that would be linked solely to the agent and not to the nature of the thing and its common utility in the society.
11Utility sometimes refers to the good, in the sense of what can have a use (S. T., IIa IIae, q. 77, a. 3, ad 1 and 2). However, when Aquinas speaks of the utility of goods given by God (S. T., IIa IIae, q. 78, a. 1, ad 1), he is referring more to the general advantage they represent for men. Generally, the notion of utility is more often linked to the operation than to the good. Thus trade is practised “for the public utility [propter publicam utilitatem]” which is supply (S. T., IIa IIae, q. 77, a. 4, resp.), and a loan can be made for “a certain utility” (De malo, q. 13, a. 4, obj. 15).
12Exchange takes place for utilitas, i.e. in the general interest of the parties. This interest corresponds to the satisfaction of a need (indigentia), since exchange takes place when each agent needs (indiget) what the other possesses (S. T., IIa IIae, q. 77, a. 1, resp.). Two elements argue in favour of a restrictive understanding of the satisfaction of needs, and therefore of the object of exchange, to what is necessary, to the exclusion of what is superfluous.
13On the one hand, this need carries a connotation of lack, as evidenced by the verb indigere, “to lack”. Even today, the indigent are the poor, those in need. Aquinas thus refers to the buyer who has great need (multum indiget) of a good or the seller who suffers harm (laeditur) by disposing of it (S. T., IIa IIae, q. 77, a. 1, resp.). The possession of the object thus takes on a form of necessity. While Aquinas witnessed the development of fairs and European trade routes, which he describes in De emptione et venditione ad tempus (1262) through the example of Tuscan merchants going to the fair at Lagny, he does not describe any increase in needs caused by the arrival of new products from elsewhere, as there would be today when caused by international trade, fashion or advertising.
- 5 “Necessaries and conveniences of life” (Smith, [1776] 1976, 1).
14On the other hand, in all his texts dealing with supply, which justifies the activity of merchants, Aquinas insists on the notion of necessity (necessitas). This necessity is not imposed by an external constraint that would be the limitation of natural resources, since Aquinas writes at a time when the very notion of resources does not exist (Arnoux, 2023), but it is thought of from the intrinsic limitation of needs. Thus from the Commentary on the Sentences (1254-1256), through De regno (c. 1265) to the Summa theologiae (1272), we find the expressions “the necessaries procured for the people” (In IV Sent., d. 16, q. 4, a. 2, qc. 3, obj. 1) and “things necessary for life” (De regno, II, 7 (II, 3) and S. T., IIa IIae, q. 77, a. 4, resp.) in order to legitimise trade. Unlike in the first sentence of Adam Smith’s Wealth of Nations, five hundred years later, we are concerned not with the things that are “convenient” to life, but only with those that are “necessary”.5
15Aquinas, however, distinguishes between two kinds of necessities: the first is that “without which a thing cannot exist [sine quo aliquid esse non potest]”, that is, that which allows one only to live. The second is “that without which one cannot live according to one’s condition or personal state [sine quo non potest convenienter vita transigi secundum conditionem vel statum personae propriae], and according to the demands of the other persons for whom one is responsible” (S. T., IIa IIae, q. 32, a. 6, resp.). Necessity can therefore be understood in a much broader sense than mere survival, coming closer to the notion of “conveniences” evoked by Adam Smith. In addition, Aquinas countenances the non-limiting and expansive character of this second necessity, to which much can be added (multis additis) to the limit (terminus). The introduction of the notion of necessity into economic activity does not therefore lead to a survival economy that would be limited to a minimum level of activity. The satisfaction of needs does not only concern vital needs but all those that are appropriate to the person’s situation. The unlimited nature of the second kind of necessity also makes it possible to envisage a change in this necessity and is not incompatible with the fact that goods that did not exist or seemed luxurious in the past now seem necessary to the greatest number.
16In his discussion of economic matters Aquinas does not specify what kind of necessity he is referring to; however, it is reasonable to consider that it is an intermediate form, involving a limitation, for his usage falls within the semantic field of indigentia, which evokes poverty by reference to the indigent, and by raising questions about one’s ability to feed oneself and one’s family (sustentare). This is found in particular in the Summa theologiae, where the mission to fill a lack is conveyed by the three good purposes of the activity of merchants and seems oriented towards a strict necessity. Firstly, this activity “is ordered to the sustentation of one’s family [ordinat ad domus suae sustentationem]”. Sustentatio comes from the verb sustentare, which means to support or nourish, but with a connotation of struggle against poverty or pain and of endurance or patience; sustentatio thus means providing your family with enough to live on, without anything superfluous. Secondly, it is about helping the indigent (indigentibus). Finally, it ensures that “the things necessary for life [res necessariae ad vitam] are not lacking [ne desint] in the homeland [patriae]”, with a lexical emphasis on both necessity and lack. We have also noted that this is where “public utility” resides (S. T., IIa IIae, q. 77, a. 4, resp.), rather than in material accumulation or the satisfaction of new needs.
17It can be seen, then, that the needs-based approach to economic activity implies it has intrinsic limitations, since the growth of such activity is not an objective in itself but is subordinate to its mission, which is to provide the necessities of life. No judgement is made concerning the level or volume of the activity of exchange; that is to say, there is no apology either for its growth or for its limitation (or for its degrowth). Rather, exchange is merely an instrument employed with a view to achieving an objective, situated on the consumer’s side, which is subject to a limit: needs must be satisfied, but needs are also finite and envisaged as elementary, with no accumulation of superfluous items.
18Economic activity is thus approached through the consumer’s need and not, as will be more common in the modern era, through the producer’s gain (Steiner, 1992, 105). Profit is only envisaged as a means of satisfying needs through exchange, and must remain moderate. This moderation appears in two lexical forms: directly, through the expression ‘moderate gain’, and indirectly, through the price controls stemming from Roman law.
19The first way in which moderation is formulated is through the use of the expression “moderate gain [lucrum moderatum]”. Exchange “for gain [propter lucrum]”, i.e. professional commercial exchange as opposed to the natural exchange engaged in by the owner of an estate, can be licit if it is carried out with moderate gain and with a view to the three good ends of supporting one’s family, helping the poor or supplying the country (S. T., IIa IIae, q. 77, a. 4, resp.). Profit is necessary for the merchant to pursue his activity and for these ends to be achieved, but these ends are not the only criterion of licitness; the moderation of profit is a cumulative criterion, as if intended to limit his bargaining power.
20The notion of moderation also appears to apply to the remuneration of lawyers and doctors (S. T., IIae IIae, q. 71, a. 4, resp.; Januard, 2025a, 266). Although the remuneration of lawyers was already regulated at the time of the Roman Republic to prevent the risk of corruption (Melkevik, 2019, 105-107), it seems that the moderation sought by Aquinas is based rather on the social necessity of the professions concerned, since among the elements entering into the calculation of what can be charged, Aquinas mentions the financial capacity of the client. The insistence on moderation can also be explained by the strong bargaining power represented by this social necessity and by the scarcity of the lawyers and doctors and the knowledge they possess.
21The second expression of the moderation of profit is the limitation on price. There is a legal supervision of commercial activity, which must be carried out “without fraud and according to a licit contract” (In IV Sent., d. 16, q. 4, a. 2, qc. 3, resp.). This broad expression appearing in the Commentary on the Sentences is gradually clarified in subsequent works. Approximately five years later, De emptione clarifies the expenses—such as transport costs—that the merchant can include in the price, and the expenses that he cannot—these are illicit expenses such as the cost of an interest-bearing loan, or imprudent expenses.
22On the one hand, Aquinas is unusually severe against merchants who borrow money to expand their business, not only because this gives usurers an opportunity to sin, but also because “the need they advance [ponitur] to live more honourably and expand their trade is not such a necessity as to exempt them from this sin” (De emptione, III). The crucial factor here is the way in which the investment is financed, with an insistence on the prohibition of loans at interest, especially since the borrower is not in a situation of necessity (Januard, 2023, 658-659); as an alternative, Aquinas proposes the model of societas (S. T., IIa IIae, q.78, a. 22, ad 5), i.e. equity investment, to finance the activity (Spicq, 1935, 349-351; Ege, 2014, 203; Chaplygina and Lapidus, 2016, 37; Januard 2022b, 246-249). One might think that Aquinas considers a certain circumvention of the ban on interest bearing loans to finance the activity through the possibility of extrinsic titles. Indeed, Aquinas accepts the possibility of the pœna conventionalis (De malo, q. 13, a. 4, ad 14) in the event of late repayment, or the damnum emergens (S. T., IIa IIae, q. 78, a. 2, ad 1), to compensate the lender for a prejudice that the deprivation of the loaned sum would cause him to suffer, but it is mainly the non-professional lender. Yet, he refuses the lucrum cessans, which would aim to compensate the lender for the gains he might otherwise have made with the sum loaned. Moreover, the extrinsic title remains formally external to the loan and is not presented by Aquinas as a source of income, but rather as compensation. The loan, even with an extrinsic title that would in a way circumvent the prohibition of interest, does not therefore constitute for Aquinas a means of financing production, and the ban of interest bearing loans contributes to encourage agents to be innovative, thought the societas (Januard, 2026), but also to moderate the development of the activity. However, beyond the nature of the financing, Aquinas’s formulation of the merchants’ claim (he uses the term ponitur, which can be translated as “they allege”), leads us to read this passage as a criticism of the immoderate and risky development of their activity, which they demand not with a view to supplying others or acquiring necessary things, but to live “more honourably [honorabilius]”, hence with superfluous comfort.
23On the other hand, still in De emptione, III, Aquinas castigates imprudent spending, whether incaute (through lack of attention) or imprudenter (through lack of foresight). He thus highlights the two dimensions of mismanagement that can lead to a price that is abusive: negligence and incompetence (Januard, 2022b, 249-261), both of which can cause a lack of cost control. One dimension of this price approach also concerns the moderation of quantities, which must be adjusted to needs. Indeed, imprudence would manifest itself in particular by an initial order that is too large, not anticipating the level of final demand at the place of resale.
24Finally, in the Summa theologiae, ten years after De emptione, Aquinas specifies the framework of the price: “the law obliges to reimburse [cogit ad restituendum], for instance, if someone has been deceived for more than half of the just price” (S. T., IIa IIae, q. 77, a. 1, ad 1). This framework takes up the ancient and medieval rule of duplus, which consists of selling a property between half and double its purchase value. Concerning its upper limit this rule is based on the notion of turpe lucrum, dishonest gain, characterising a resale at more than double the initial price, and for its lower limit on the notion of laesio enormis, which in Ancient times protected the seller of land, which a buyer could not buy for less than half of its value (Januard 2022c, 80-84). The gain is therefore limited by the price.
25The moderation of gain is thus expressed in Aquinas’s work through a variety of expressions. For the supplier there is the same need of sobriety as for the consumer, whose needs are limited to necessity; and, in addition, that gain should be moderate confirms its instrumental character within a needs-based approach to activity. Thus while Aquinas does not directly approach economic activity from the perspective of the place of human beings in their natural environment, all agents such activity is subject to a certain sobriety. It is driven by the need for necessary things and the gain from it is justified only if it is moderate and accompanied by good management of costs and investments. This approach avoids deprivation and scarcity on the one hand, and on the other hand prevents the development of economic activity through the maximisation of the producer’s and seller’s profits driven by the creation of new needs. And since activity is limited, so is the use of natural resources.
26Aquinas addresses the necessity of supply in several texts, and presents its two sources: local sourcing and importation. The risks of transport and the negative social influence exerted by foreign merchants then lead him to support not only local supply, but a form of ‘short supply chain’. Indeed, he only mentions merchants in terms of imports, but not local supplies. It can be assumed that this local supply is carried out in the mode of natural exchange (S. T., IIa IIae, q. 77, a. 4, resp.), directly by the master of the household (œconomicus), the craftsman, involving no or few intermediaries and no great merchants.
27Although his motivation is not to preserve the environment nor to take into account a general scarcity of natural resources—although some regions are more fertile than others—this preference for the ‘short supply chain’ does, however, resonate with contemporary supply models put in place with an ecological goal in mind. Since regions are not entirely self-sufficient, he does not advocate autarky but rather a balance that allows us to benefit from the contribution of merchants in terms of satisfying needs, while limiting the cultural and social damage they cause.
28Aquinas asserts the licitness of trade for supply in the first lines of his first text on the activity of merchants (Januard, 2022c, 56 and 66; 2023, 652 and 672). In fact, he specifies in Objection 1 of this text in the Commentary on the Sentences (1254-1256) that trade (negotiatio) is “that by which the necessary things are procured for the people [per quam necessaria populo procurantur]” (In IV Sent., d. 16, q. 4, a. 2, qc. 3, obj. 1). The respondeo of this article does not contest the objection and is limited to giving the conditions for the licitness of trade, according to three criteria—person (persona), time (tempus), mode (modus)—which Aquinas borrows from his master (Albert the Great, In IV Sent., d. 16, a. 46): trade is forbidden to clerics and monks, it can only be carried out on the days appointed, that is to say not on feast days, and it must be done “without fraud and according to a licit contract” (In IV Sent., d. 16, q. 4, a. 2, qc. 3, resp.). He again takes up the argument of provisioning in the Summa theologiae (1272), at the end of his life, when he considers that the professional activity of merchants can be carried out for three good purposes: to support one’s family, to provide for the needy, and to provide the country with the necessities of life (S. T., IIa IIae, q. 77, a. 4, resp.).
29The economic section of De regno presents two arguments arguing for the necessity of international trade, both from the point of view of imports and from the point of view of exports. As it has already been found in the Commentary on the Sentences and would be found later in the Summa theologiae, trade is first necessary for the supply of goods:
Merchants should not be completely excluded from the city, because it is not easy to find a place that is full of all the things necessary for life. (De regno, II, 7 (II, 3))
30While several of Aquinas’s texts emphasise the importance of trade for the supply of goods, De regno also stresses the need for it to ensure outlets for local overproduction:
The abundance of goods that are in too great a quantity in one place would in the same way bring great harm to many, if these goods could not, through the function of merchants, be transported to other places. (De regno, II, 7 (II, 3))
- 6 “The annual labour of every nation is the fund which originally supplies it with all the necessarie (...)
31De regno thus gives the two reasons that justify international trade: supply, which appears in Aquinas’s other texts, but also the need to find outlets for the surplus produced locally. Although the articulation within the same mechanism has not yet been established by Aquinas, the two structuring elements of the modern and contemporary approaches to international trade are thus in place. As a paradigmatic example, they appear in the first sentence of Adam Smith’s Wealth of Nations, since what is locally produced is either consumed directly or sold to buy other products from other nations.6
32Aquinas remained cautious, however, with regard to merchant activity and international trade. De regno thus rules by a cautious acceptance of necessity (Franks, 2009, 102; Hirschfeld, 2018, 143):
This is why a perfect city must use merchants with moderation [moderate mercatoribus utatur]. (De regno, II, 7 (II, 3))
- 7 Although certain details of Aquinas’s life and certain dates are still debated, biographers agree o (...)
33His view of merchants is ambivalent. Coming not from a family of merchants but of knights (Weisheipl, [1974] 1993, 16-19; Synan, 1988; Torrell, 2015, 20-25), for Aquinas the merchant, like the peasant, is of subordinate rank (S. T., Ia IIa, q. 91, a. 6, resp.); however, having rubbed shoulders with traders during his journeys between Italy, Paris and Cologne,7 he is more tolerant regarding the licitness of trade than were Gratian and Peter Lombard a century earlier (Januard 2022c, 60-61).
34Aquinas retains six reservations in De regno, II, 7 (II, 3), which sound like so many risks of trade for the city:
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A risk of dignity, since a thing is more dignified (dignius est) if it is self-sufficient, and it is more dignified for a territory not to depend on another. It should be noted here that there is a break in the consonance between Aquinas’s thought and the ecological approach. Indeed, the former emphasizes independence while the latter promotes interdependence within an environment;
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A supply risk, because economic independence is safer (securius) for supplies, “because of wars and the various critical risks along the way [diversa viarum discrimina]”, such as shipwreck or robbery. The risk of transport is expressed through the lexicon of danger, here by ‘discrimina’ (critical point of a danger), and a few years later in the Summa theologiae by the common name for danger, periculum (S. T., IIa IIae, q. 77, a. 4, ad 2; Januard, 2024a, 432-436);
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A risk of cultural corruption, because trade brings people into contact with foreigners, whose company most often corrupts the morals of citizens (extraneorum conversatio corrumpit);
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A risk of moral corruption because “if the citizens themselves indulge in commerce [si cives ipsi mercationibus fuerint dediti], the door will be open to many vices”: everything will become venal in the city (ut in civitate omnia fiant venalia), which will find itself open to fraud (locus fraudibus apertitur);
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A military risk with the weakening of the army if soldiers indulge in commerce, whose characteristics soften the soul and render the body debilitated;
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A political and public order risk, since trade encourages gatherings, which are conducive to strife (lis) and sedition (seditio).
35A city’s dependence on imports presents two types of risk: the economic risk of shortages resulting from war, shipwreck or robbery, and the political and cultural risk of foreign merchants having a bad influence on the population. This led Aquinas to prefer local supply:
It is obvious that the first means [local supply] is the most advantageous … because that which needs something else shows that it is deficient. However a city is much more self-sufficient, when the surrounding region provides it with the things necessary for life, than when it needs to receive them from others through trade. (De regno, II, 7 (II, 3))
36Aquinas’s criticism should be seen in the context of the thirteenth century, which saw the development of major trade routes in Europe, not only maritime routes from major ports, but also land and river routes between Flanders and Venice and along the Seine valley (Ellul, 2013, 201). Regular major fairs, particularly in Champagne, set the pace for Europe’s economic life and the lives of merchants: Lagny in January-February, Bar-sur-Aube in March-April, Provins in May-June, Troyes in July-August, Provins in September-November, and Troyes in September-November (Le Goff, [2010] 2019, 30). The fairs were institutions with legal personality and privileges (Ellul, 2013, 222-224). It was a time of urbanisation and the rise of towns, with their crafts, trade and local markets (Ellul, 2013, 224-225), and the birth of a new social class, that of professional merchants, well versed in accounting, foreign exchange, navigation and commercial law; yet the scope of their activity was still unclear, which could lead to usurious suspicions (McLaughlin, 1939, 75-95; 1940, 1-22; De Roover, 1953, 28-29; Le Goff, [1956] 2001, 41-67; [2010] 2019, 121-231; Ege, 2014, 392; Feller, 2020, 57-61). The development of long-distance trade thus represented a new political, economic and social challenge, both as a source of supplies and enrichment and as a source of new risks for the society.
37The economic risks—shortage—and social risks—bad influence of merchants—identified by Aquinas, combined with the need for trade, are thus part of the changes experienced by his era. We can, however, read in his work a more universal analysis of the relationship between the two sources of supply, local and more distant. Although the context has changed dramatically in eight hundred years, the need to provide for the population’s needs, and the recourse to trade, continue to structure social life today. Aquinas wrote more than five centuries before the advent of international trade theory, inaugurated by the highlighting of the absolute advantage by Adam Smith ([1776] 1976, IV, ii, 12), then the comparative advantage by David Ricardo in On the Principles of Political Economy and Taxation ([1817], 1999, VII), and the many developments of the Heckscher-Ohlin-Samuelson theorem in the mid-twentieth century. However, De regno raises five questions concerning the place to be assigned to trade in the structuring of supply—questions that are still asked today in economic policy trade-offs, and that remain beyond historical contingency.
- 8 This is in line with the current development of concepts such as “human ecology” (see, for instance (...)
- 9 These two sources of commercial disorder—disputes between traders and sedition—are echoed in the pr (...)
- 10 On researches on the limits of the market and commodification studies, see Radin (1987; 1996), Stei (...)
38The first risk is that represented by external dependence in terms of supply, but also the risk posed to outlets by wars and everything that threatens transport. The second concerns the ecological issue. Aquinas’s motivation is the preservation not of the planet but of a social, political and cultural order; yet this can indeed be considered part of a broad understanding of the notion of the “surrounding external world” as used in the original definition of ecology (Haeckel, 1866, 286), which would then refer to human beings’ relationship with their environment, conceived not only as natural but also as social.8 The third concerns the disturbance of public order resulting from commercial disagreements during gatherings of merchants, which can generate unrest or conflicts with the feudal authority. Traces of such disturbances remain in contemporary popular culture.9 The fourth concerns the cultural corruption engendered by the arrival of merchants, which Aquinas attributes to such people’s behaviour. It might be noted that the foreign merchants Aquinas mentions in his texts (De emptione) are Italians at the fairs in Champagne; yet Aquinas evokes cultural corruption despite the fact that the merchants and the populaces of the cities they frequent practice the same religion, possess a common formal language, and speak very similar vernaculars, and that Aquinas himself, as an Italian having crisscrossed Europe and lived in the Latin Quarter of Paris, was himself both an observer and a participant in the cultural mixing underway in medieval Europe. The corruption therefore probably stems more from the profession itself than from the merchants’ foreign origins. Cultural corruption can also take place at the level of the goods sold than at the level of the people, through a standardisation of consumption practices to the detriment of the valorisation of local products. The fifth lies in the commodification of the entirety of social life and the fear that everything will become venal: this phenomenon of commodification, observable in Aquinas’s own thought (Januard and Lapidus, 2023), finds multiple contemporary echoes.10
39It is difficult to assess the influence of mercantile society on the thought of Aquinas, who travelled the same routes as the merchants and witnessed the rise of this new social group. However, we can see that Aquinas himself engaged in a twofold form of commodification, and precisely for the least commodified of goods, namely the spiritual good, the sale of which constitutes the sin of simony (Januard, 2022a, 582-585; Januard and Lapidus, 2023, 127-130). On the one hand, Aquinas operates a partial commodification, because the spiritual good, which “cannot be the object of a price [non cadit sub pretio] (In IV Sent., d. 25, q. 3, a. 1, qc. 1, resp.), still may be exchanged with a counterpart which is a subsistence allowance enabling the priest to live: “[the priest] can receive money … not as the price of a mass [pretium missae], but as a means of subsistence [quasi sustentamentum vitae]” (In IV Sent., d. 25, q. 3, a. 2, qc. 1, ad 4, see also S. T., IIa IIae, q. 100, a. 2, resp.). Here we find what today corresponds to a ‘tariff’ or a stipend permitting the operation to be repeated (Steiner and Trespeuch, 2014). On the other hand, Aquinas operates a lexical commodification: addressing sacraments in the Summa theologiae, while maintaining the impossibility of a price as in the Commentary on the Sentences, Aquinas now also expresses this impossibility in terms of the level of price and not of its presence per se: “If it were sold, then a great thing would be sold at a low price” (S. T., IIa IIae, q. 100, a. 3, ad 2; see also q. 100, a. 1, resp.; in addition, on the impossibility of selling a free man, see q. 189, a. 6, ad 3).
40It emerges from this perspective on Aquinas’s position on trade that, for him, the issue was not that of choosing between autarky and free trade. Rather, it was a question of arbitrating between a preference for a certain degree of local autonomy and an appreciation of what was produced locally, and excessive foreign dependence, which also meant dependence on large-scale trade and professional merchants, who traded “for gain”. Their influence can be detrimental; however, they perform a social function of supplying through imports, but also of exporting, contributing to the prosperity of the city and satisfying the needs of other cities. So there is a preference, though not an exclusive one, for local production and ‘short supply chains’, and a caution, allied to a recognition of necessity, towards international trade.
41This balance advocated by Aquinas is not motivated by respect for the natural environment, yet for two reasons can be described as ‘ecological’ nevertheless: Firstly, while the motivation for this position is not ecological in the strict biological sense, it is ecological in a broad sense that attributes a social and cultural dimension to the notion of ecology. Secondly, this position can be read and received today as consonant with the contemporary valorisation of short supply chains on ecological grounds.
42Aquinas’s approach is not only characterised by an emphasis on local sourcing, by choosing in advance the mode of supply that is most respectful of the planet. His approach takes an epistemological approach to delimiting human activity, which today we would describe as economic, by limiting this activity to transformation, transport and exchange to satisfy needs. The use of the lexicon of production means, as in classical Latin and the biblical tradition, that only the earth produces: human beings simply adapt to the fertility of the earth by settling in a particular place and then receiving what nature gives them. Their mission of satisfying needs fairly through crafts, agriculture and trade therefore remains subordinate, in an act of reception rather than capture, to the production given to them by the earth.
43The economic passage of De regno promotes short supply chains, advocating a balance between local production and the imports and exports that are necessary for subsistence. However, greater attention to the lexicon allows us to offer a deeper reading of the place of human economic activity within the natural environment:
But there are two ways in which a city can be assured of an abundance of things. The first … comes from the fertility of a region producing [producentis] in abundance all that the necessities of human life require. The other comes from the use of trade by which the goods necessary for life are imported [adducantur] from various regions into the same place.
(De regno, II, 7 (II, 3))
44This is the only occurrence in Aquinas’s economic writings of the verb producere (to produce) taken in an economic sense; it therefore stands out from other instances of the word that sprang from his pen. For instance, he often uses ‘production’ in its metaphysical sense (see e.g. Prieto, 2021); and in his non-economic texts, but in a more economic sense, we find the idea of cooperation in the work of production between man and nature and of the active role of man as producer, especially through the arts (e.g. in In I Sent., d. 6, q. 1, a. 2, s. c. 1), although the word “productio” does not always appear. We also find another occurrence of the verb producere in his economic texts, in the question on commercial exchange in the Summa theologiae, with respect to alchemy:
If true gold were made [fieret] by alchemy, it would not be illicit to sell it, for nothing forbids the art of using certain natural causes to produce [ad producendum] natural and true effects. (S. T., IIa IIae, q. 77, a. 2, ad 1)
45Aquinas does not deal with alchemy to distinguish between what comes from nature and what comes from human beings, but to address the issue of the nature and usefulness of a good, according to whether the gold produced is true gold or not and has the same properties. However, the passage brings an element specific to the production process. In this text, human beings play an active role, although it is natural causes that allow the effect to be produced. Three elements call for caution. Firstly, the lexicon of cause and effect is more philosophical than economic. Secondly, the introduction with “if” and the use of the subjunctive “fieret” reinforce the hypothetical nature of the action and its outcome. Finally, the activity described is not the manufacture of material goods for sale.
46De regno’s use of the verb producere has a singular character. Aquinas distinguishes between “a region producing [producentis]” and “the use of trade by which the goods necessary for life are imported [adducantur]” (De regno, II, 7 (II, 3)). This distinction introduced in De regno calls for two comments. On the one hand, the two verbs indicate actions in opposite directions, but actions which are not contrary. The verb producere, which means “to draw towards”, “to lead forward” or “to bring”, is in directional opposition to adducere, “to bring to oneself”. However, although adducere can be translated as “to import”, exporting would be more like “exportare”. So we are not talking about two actions that oppose or cancel each other out, but rather two distinct movements that are not opposites. On the other hand, the verb adduce is used in the passive, with the implicit agent being the subject of the use of trade (mercationis usum), i.e. the traders and those who command and organise this trade. The active agent who ‘produces’ is the region, i.e. the land, in the broad sense of all natural elements. What is at stake in the distinction between the two expressions is not, therefore, a tension between import and export, but a distinction between complementary actions that have different agents: the land produces, human beings transport. The active role of the land is reinforced by the fact that the notion of wealth, capacity to produce, or fertility, designated by the term ubertas, is attributed to the city, not to people. Indeed, it is “through its wealth [ubertate]” that the city can feed its population (De regno, II, 7 (II, 3)).
- 11 Even in the early seventeenth century, production was still that of the land and natural elements, (...)
47Although the notion of “production” did not take on its contemporary economic meaning until the modern era, and particularly from the end of the seventeenth century with Pufendorf and Boisguilbert, its inclusion in Aquinas’s economic lexicon has epistemological implications.11 Producere may have taken on the modern meaning of “to produce” in the sense of “to fabricate” because it is a question of leading to somewhere else, hence the idea of leading to life or existence. It is therefore easier to understand why, in the Bible and in Aquinas’s works, it is an eminently divine action or natural generation, like the tree that produces fruit. Aquinas takes up the classical meaning of the verb producere and uses it in relation to economic activity, which is a human activity, but production is upstream and firstly remains the work of nature. However, Aquinas envisages action being undertaken by the human being to promote this production of nature through the care given to the tree and, more generally, in agriculture (Compendium theologiae, l. 1, cap. 140, resp.; Super De Trinitate, pars 3, q. 5, a. 1, ad 5). Human action should therefore not be discounted in promoting production by the land.
48Aquinas is following the biblical tradition, since in the Vulgate the verb producere has man as its subject only to describe a physical forward movement. In the book of Genesis, the use of the verb in the semantic field of creation is reserved for describing actions whose subjects are the natural elements that act at God’s command. This is the case with water: “And God said, ‘Let the waters bring forth living creatures that creep and fly upon the earth under the firmament of heaven’” (Genesis 1:20, see also v. 21). The same is true of the earth: “God also said, ‘Let the earth bring forth every living creature according to its kind, beasts of burden, creeping things and wild animals according to their kind’. And so it was” (Genesis 1:24). God himself produces, as in the case of the tree of good and evil: “The Lord God produced out of the ground every tree beautiful to behold and good for food: the tree of life in the midst of paradise, and the tree of the knowledge of good and evil” (Genesis 2:9). Conversely, man does not “produce”. In the New Testament, the two Gospel occurrences of producere are applied to trees, which produce fruit (Mark 4:29 and Luke 21:30), and the Acts of the Apostles uses the verb with the human being as subject, but in its original sense of displacement, to mean “to bring before justice” or “to lead to the beasts” (Januard, 2024b, 524).
49In De regno, the verb producere has a subject in the active tense (the region) and a complement (what is necessary for life). The sentence places more emphasis on the action, its subject and what it produces, than on the addressee. The emphasis is on the act of production rather than its use. What is more, lexically it is a kind of state of nature, following the order of creation described in Genesis before the intervention of man, who is not created until Genesis 1:26. Production therefore precedes human activity scripturally and temporally (in the biblical temporality).
50De regno does not, therefore, merely give an account of a discussion on the respective benefits of two human activities, local trade and long-distance trade, which enable supplies to be obtained, or even of an appreciation of human production in relation to trade. It is also, according to the letter of the Thomasian text, a discussion between the production of nature, in which human intervention is possible but not mentioned, as if it were secondary, and a specifically human activity, trade. This natural conception of production is confirmed by the entire passage in De regno, since local supply is never explicitly the result of human intervention. The subject of supply, like that of production, is always the region: “a city is more self-sufficient when the surrounding region is sufficient for the things necessary for life” (De regno, II,7 (II, 3)).
51Natural resources are therefore the primary determinant of all human activities. Here there is an enlightening contrast with the physiocrats, who are sometimes seen as reminiscent of the medieval authors in their relationship with the land, the source of all production, and by the idea of cyclical economic activity, through the seasons, and in the Middle Ages the cycle of fairs. For the physiocrats, human intervention was now a determining factor, and the relationship of domination more assertive. Thus, in his explanation of the Tableau économique (1758), François Quesnay presents the number of men needed to “exploit [exploiter]” a certain number of arpens of land and describes the means employed (oxen and ploughs) and the nature of the expenses (cattle, tools, seeds, food, maintenance, salaries), but the role of the land is passive (Quesnay, [1758] 1894, VI). It is no longer the land that provides man with his sustenance, but man who draws it from the land.
52Conversely, Aquinas presents economic activity as what we would now call an activity of maximisation under constraint, the constraint being not primarily financial but natural: it is not about exploiting or pushing the limits of nature, but about adapting to what nature provides. His presentation of economic activities could tempt us to an anthropocentric reading, since he does not explicitly deal with natural resources; however, this is not because the limits imposed by these resources are negligible, but on the contrary because they provide a framework for human activity in which they are given and primary.
53Given that the land is productive, De regno begins by mentioning an initial preliminary activity, before embarking on the process of exchange. The human being chooses the place where he establishes the city according to the productive capacities of the land, which precede him and remain primary:
The place chosen for the construction of a city must not only be such as to preserve the inhabitants by its healthiness, but also such that, by its wealth, it is sufficient to feed them. (De regno, II, 7 (II, 3))
54This preliminary activity was not conceived as being undertaken by individuals or families, but rather as being of a political nature, since it concerned the place where the city was established. This sheds new light on Aquinas’s economic approach. Whereas this approach is mainly located at the level of the justice of singular exchange, De regno underlines the political foundation that underlies all the economic activity constituted by these exchanges.
- 12 Ethicorum written around 1250-1252, ed. Cologne, V, VII, 403-404 and V, IX, 413, and Ethicorum writ (...)
55Aquinas usually deals with economic activity in an individual context, as between two contractors, although he sometimes evokes the intervention of the prince, as in the case of money, the value of which results from an agreement between men or from the will of the sovereign (Politicorum, I, 7) and whose name numisma comes from nomos, the law (Ethicorum, V, 9), or the determination of measures to guarantee the justice of exchange (S. T., IIa IIae, q. 77, a. 2, ad 2). In the Letter to the Duchess of Brabant he also envisages the whole city, since after having tried to restore the tax levied on usurious gains to the victims of usury, the prince can allocate it to “pious uses with a view to the common good”. However, Aquinas most often features a seller and a buyer, a lender and a borrower. The prince intervenes in the value of the currency, but its invention was the work of the contracting parties themselves to facilitate trade (Politicorum, I, 7; Ethicorum, V, 9). Moreover, where one would expect a more social and political vision, Aquinas limits his analysis to the contracting parties. Unlike Aristotle (Nicomachean Ethics, V, 5, 1133a) and even more so Albert the Great, who insists on it in his two commentaries,12 Aquinas does not draw the consequences of the cessation of exchange between craftsmen resulting from a price that would not cover the costs of production “in labour and expense” (Ethicorum, V, 9) and does not specify that this would lead to the end of craftsmanship and, as Albert points out in a long development, to the collapse of the city (Hamouda and Price, 1997, 195). Aquinas’s question is more about the justice of exchange than about its political and social implications.
56We can thus see economic activity as a process that unfolds from the common to the singular: production comes from the land, it gives rise to a political and collective decision to choose the place of installation, and this then allows the individual development of processing, transport and exchange activities. If we then adopt a contemporary meaning of terms in which the economic would encompass all that Aquinas calls voluntary exchanges (S. T., IIa IIae, q. 77, prol.; Januard, 2022a), i.e. both natural exchanges and exchanges for profit (S. T., IIa IIae, q. 77, a. 4, resp.), and the ecological would designate what is given by nature, we can thus posit that on Aquinas’s account, the economic is subordinate to the political, which in turn is subordinate to the ecological. Subordination is understood here as a submission to conditions of possibility. The first human activity is therefore an activity of adaptation, which aims to make maximum use of the earth’s abundance so that the satisfaction of needs is also maximised. The process of exchange for the satisfaction of needs is subordinated to the activity of adaptation, which in turn is subordinate to the fertility of the earth.
57Once the city is established, human beings transform, transport and sell. However, Aquinas never shows interest in the activity of processing for its own sake, but only to specify the income of the manufacturer or to show him as a stakeholder in an exchange relationship.
58In the Summa theologiae, Aquinas evokes the different types of income. He distinguishes first of all between persons who practise “natural and necessary” exchange (naturalis et necessaria), “for the necessities of life” (propter necessitatem vitae), such as “the masters of the household [œconomicos] or the heads of the city [politicos]”, and the merchants who trade “for gain” [propter lucrum] (S. T., IIa IIae, q. 77, a. 4, resp.). He then distinguishes between simple merchants and merchant craftsmen (who improve the good), the former receiving income “as an indemnity for their work” (quasi stipendium laboris), the latter receiving income as a “premium” (praemium), involving an idea of proportionality arising from the fact that the merchant craftsman improves (melioravit) the good (S. T., IIa IIae, q. 77, a. 4, resp. and ad 1 and 2).
59Craftsmen only appear as manufacturers in the Commentary on the Nicomachean Ethics. There we find the cutler (fabricatio cultelli) and the house-builder (aedificator), the shoemaker (coriarius), the physician (medicus) and the farmer (agricola), and then allusively wine-growers, since their activity involves exchanging wheat (frumentum) for wine (vinum). It should be noted, however, that Aquinas only refers to the “action of the craftsman” (actio artificis) in order to consider the relative prices and conditions of exchange of goods, not to deal with the professions themselves (Ethicorum, V, 8-9). Craftsmen are therefore presented only in terms of the commercial aspect of their activity.
60Two fundamental clarifications thus emerge. First, as we have seen, there is only one category of things as an object of exchange, namely necessary things, whether imported or locally produced, whether foodstuffs or manufactured goods. Secondly, there is no clear separation between the professions of manufacturing and marketing, or between agriculture and crafts. On the one hand, Aquinas, the son of a knight, associates peasants with merchants, as well as craftsmen, as they are involved in exchange. On the other hand, we here witness a kind of unification, at least partially, of the activities of the peasant, the craftsman and the merchant, who transform, transport and sell what initially comes from the land. The improvement of the good by the merchant-craftsman and its simple transport by the merchant gives rise to a distinction that relates to the nature of the income, but all human activities are downstream of the production of the land.
61Economic activity is plural, depending on whether one transforms the fruit of the production of the land as a peasant or craftsman, whether one transports and sells these commodities as a merchant, or even whether one lends money as a usurer. The income received, the goods and services produced, and the names of the trades may differ; however, as a whole it amounts to a unified set of human activities consisting of receiving the production of the land to satisfy needs through exchange. These activities are thus unified and reduced both by their condition of possibility, namely production, which is the object of at least local scarcity since no land produces everything, and by their purpose, the satisfaction of needs and not unlimited gain. Aquinas’s attention to the justice of exchange therefore does not consist in making this exchange an absolute, but in ensuring this exchange takes place under conditions that respect a triple boundary: its source, i.e. natural resources; its conditions of exercise, which take the form of an inaugural gesture of economic policy, i.e. the choice of the place where the city will be located; and its end, the well-being of the human being.
- 13 Man thus finds his role within creation, since he receives the goods of Providence through the prod (...)
62The first human activity is therefore one of adaptation, aimed at making the most of the earth’s abundance so that the satisfaction of needs is also maximised. The process of exchange for the satisfaction of needs is subordinate to the activity of adaptation, which is itself subordinate to the fertility of the earth. The justice of exchange aims to ensure the distribution of production given by nature to satisfy needs. This justice concerns the remuneration of the services of transformation, transport and sale. We can therefore better understand the importance of the notion of “just price” for Aquinas, since it is this price that ensures the distribution of earthly and ultimately, in his biblical and theological perspective, divine production.13 The expression “just price” appears nineteen times in his works, but the first three occurrences are not in the economic texts, but in the theological writings. The first concerns God’s communication of his wisdom to human beings in the book of the prophet Isaiah and is found in Aquinas’s early biblical commentary, probably written in 1252 (Super Isaiam, 55, 1), and the next two appear in the treatise on the sacraments in the Commentary on the Sentences (In IV Sent., d. 25, q. 3, a. 1, qc. 1 and d. 36, q. 1, a. 2). The justice of the price thus includes a sacralised dimension capable of accounting for the relationship between God and humankind, which is consistent with its function of ensuring the satisfaction of needs from production provided by the earth and ultimately by God.
63Aquinas defines price in the Commentary on the Sentences on the basis of an equality of values: “the price of a purchase is given as a measure equivalent to what is purchased” (In IV Sent., d. 25, q. 3, a. 2, qc. 1, resp.). The way in which a just price is reached remains open to debate, however, between an approach based on production costs, since the Commentary on the Nicomachean Ethics notes that the exchange only takes place if the production costs “in labour and expenditure” (Ethicorum, V, 9) are covered by the price, and an approach based on utility, since “the just price will be established not only according to the thing sold, but according to the prejudice which the seller incurs by the sale” (S. T., IIa IIae, q. 77, a. 1, resp.), translated by a market approach, since De emptione considers that there is usury, and therefore that the price is not just, if the merchants “sell the cloth for more than it is worth on the common market” (De emptione, II).
- 14 An emblematic expression of the production cost approach can be found in Tawney ([1926] 1948), and (...)
64Contemporary literature has distanced itself from this debate,14 since Aquinas moves from one of these approaches to the other, whereas commentators try to choose between these approaches, which they consider to be alternatives. This literature has focused more on highlighting the primacy of the notion of justice and the conformity of the price to the virtue of justice. This evolution in the approach to the just price seems to give a better account of the role of the price, which is to distribute justly the goods given by the land by satisfying needs through exchange. The price has to implement justice, but justice, as a virtue, pre-exists the operation and comes from the production given by nature which, in the Bible, is part of the order of creation and continues in the order of the covenant that God seals with humankind. It is thus easier to understand why Aquinas’s theological treatment of the sacraments resembles what can be reconstructed of the places where the just price is expressed (Januard, 2022d, 755-759 and Januard, 2022c, 78). Beyond Aquinas’s use of the same conceptual apparatus when addressing different subjects, we find here the internal coherence of such a close treatment, since it is always a question of fulfilling the divine plan. In fact, the purpose of exchange is to complete what was begun by the work of divine creation and then by earthly production.
65Although the notion of a “just price” is essential, it must be extended to the application of a just exchange ratio, which is not limited to price understood as the equality of values (Januard, 2025a, 250-269). Aquinas deals with the limit cases of the market within the framework of exchange, which allows them to be integrated into the whole process from production by the land to the satisfaction of needs. To do this, he proposes a plurality of exchange ratios, in order to account for the exchange of what cannot be priced. Justice therefore consists firstly in the nature of the exchange ratio being just, and secondly in its level being just. It is the nature of the good, its quid, that determines whether it can be priced or not. Thus, as we have seen, the sin of the simoniac, who sells sacred goods, is to sell what cannot be the subject of a price (In IV Sent., d. 25, q. 3, a. 1, qc. 1, resp.), but this good is nevertheless the subject of an exchange, with an exchange ratio, here of the order of a subsistence allowance, and therefore implying a counterpart (In IV Sent., d. 25, q. 3, a. 2, qc. 1, ad 4 ; S. T., IIa IIae, q. 100, a. 2, resp.).
- 15 On extrinsic titles inherited from Roman law, see the now classic references McLaughlin (1939; 1940 (...)
66This plurality makes it possible to envisage many different cases. For instance, a soldier’s work, like that of a priest, is subject to a stipend (stipendium), which is not based on a relationship of value, but is an indemnity so that he can continue to fulfil his social mission. Similarly, the merchant receives “like a stipend for his work” (quasi stipendium laboris), since it is not a wage, which would be proportional to the work done, but his income nevertheless comes from his work (S. T., IIa IIae, q. 77, a. 4, resp.). This also allows Aquinas to consider the compensation received by the lender for the loss represented by the deprivation of the sum lent, even though it is interest-free. The extrinsic title,15 which provides for a payment to the lender, establishes an exchange ratio. The latter does not, however, constitute a price but a compensation or an indemnity (S. T., IIa IIae, q. 78, a. 2, ad 1). Aquinas rejects lucrum cessans, compensation for loss of income, but he accepts damnum emergens, which stipulates compensation (recompensatio) for harm (damnum), and which generally consists in having to borrow to make up for the loss caused by the loan granted. He also refers to pœna conventionalis, whereby the borrower is “liable to a penalty for late repayment” (tenetur ad interesse) (De malo, q. 13, a. 4, ad 14). There are also transactions involving a more complex exchange ratio, which is certainly partly a price (a ratio of values), but which also takes into account other components, such as the buyer’s financial capacity. This is the case of the consideration demanded in exchange for the services of the lawyer (advocatus) and the physician (medicus), which must be moderate and not based solely on the equality of things, but “taking into account the personal condition [of their clients: considerata conditione personarum], the business [dealt with: negotiorum], the work [laboris], and the customs of the country [consuetudine patriae]” (S. T., IIa IIae, q. 71, a. 4, resp.).
67Aquinas takes exchange in its broadest sense, so that needs can be satisfied from the earth’s production. The plurality of forms of exchange ratios makes it possible to ensure the justice of the exchange in accordance with the nature of the good exchanged, since some goods are part of the price, others of a stipend. The purpose of the fair exchange ratio and, when it is accurate, of the just price, is to finalise the long process begun by the production of the land, continued by the work of the peasant and the craftsman, then by the service of the merchant, so that everyone has what he needs. The justice of exchange and the notion of a just price are therefore not only intended to ensure the justice of social relations, the absence of fraud or even a good distribution of supplies. They take on a much broader and more fundamental role. They ensure a form of compliance with the implementation of the last stage of a process of satisfying needs that began even before human intervention to ensure compliance with the initial stage, which is, like the principle, the contribution of what the earth produces. The justice of exchange is therefore an extension of the just adaptation to the abundance of the earth.
68Aquinas’s thought may seem far removed from contemporary questions in the field of ecology, since it pays little attention to natural resources, and the preservation of ecosystems is not the concern of medieval authors in general nor of Aquinas in particular. In addition, the medieval economic world is markedly different from the world today. Nevertheless, the Thomasian contribution can shed light on contemporary debates by the form of balance that it embodies and by its unifying coherence.
69First, Aquinas’s economic thought, and particularly his conception of the presence of merchants, may be seen as based on a broad interpretation of ecology according to its initial definition (Haeckel, 1866), which gives it not only a biological but also a social scope; and it is this that may have led some authors inspired by Thomasian thought to use the expression “integral ecology” or “human ecology” to translate this global approach to the relationship of human beings with what surrounds them.
70Aquinas then focuses his analysis on human activity and the satisfaction of needs, this being the goal towards which manufacture, exchange and gain are all oriented. He is therefore not concerned with limiting this need or restricting its satisfaction, nor artificially arousing it in order to achieve ever greater gain through ever greater production; it is simply a matter of satisfying necessary need. The implicit sobriety that results from this remains anthropocentric, in that it does not come from an external constraint but depends on those necessary needs.
71Finally, Aquinas limits economic activity epistemologically by making it begin, at least in the economic texts, after the phase of production by the land. The first act undertaken by human beings is to adapt by setting up their city where the fertility of the earth is greatest. In these texts, Aquinas does not envisage any action intended to control this fertility. Human beings are dependent on the contribution of the earth, the reception of which is the first step towards satisfying their needs. While economic activity itself is anthropocentric, it is nevertheless part of a whole process that begins with the natural environment.
72Aquinas thus combines a needs-based approach and a resources-based approach. The former approach is first in the order of finality, while the latter approach is first in the order of causality. It is the resources provided by the earth and their proper reception and management by human beings that make it possible to satisfy needs.
The author would like to warmly thank the participants in the sessions of the 2024 annual conference of the ESHET and 2025 annual conferences of the Association Charles Gide and the Association Française d’Économie Politique (AFEP), and the anonymous referees, for their helpful remarks and suggestions on a previous version of this article. Responsibility for the opinions expressed in this articles lies entirely with the author.