Thomas Aquinas

==Philosophy==
{{Thomism}}
{{Main|Thomism}}
[[File:Friesach - Dominikanerkirche - Hochaltar - Hl Thomas von Aquin1.jpg|thumb|Thomas Aquinas and the Pope]]

Thomas Aquinas was a theologian and a [[Scholasticism|Scholastic]] philosopher.{{sfn|Jordan|2006|p=154}} He never considered himself a philosopher, and criticized philosophers, whom he saw as pagans, for always "falling short of the true and proper wisdom to be found in Christian revelation".{{sfn|Davies|2004|p=14}} With this in mind, Thomas did have respect for Aristotle, so much so that in the ''Summa'', he often cites Aristotle simply as "the Philosopher", a designation frequently used at that time. However, Thomas "never compromised Christian doctrine by bringing it into line with current Aristotelianism; rather, he modified and corrected the latter whenever it clashed with Christian belief".<ref>{{Cite book |title=The History of Philosophy, Medieval Philosophy, from 500 to 1500 CE|year=2011|editor= Brian Duignan |publisher=Britannica Educational Publishing |location=New York|isbn=978-1-61530-244-4|chapter=Age of the Schoolmen}}</ref>

Much of Thomas's work bears upon philosophical topics, and in this sense may be characterized as philosophical. His philosophical thought has exerted enormous influence on subsequent Christian theology, especially that of the Catholic Church, extending to Western philosophy in general.

=== Commentaries on Aristotle ===
Thomas Aquinas wrote several important commentaries on [[Aristotle]]'s works, including ''[[On the Soul]]'', ''[[On Interpretation]]'', ''[[Posterior Analytics]]'', ''[[Nicomachean Ethics]]'', [[Physics (Aristotle)|''Physics'']] and ''[[Metaphysics (Aristotle)|Metaphysics]]''. His work is associated with [[William of Moerbeke]]'s translations of Aristotle from [[Ancient Greek|Greek]] into [[Latin]].

===Epistemology===
{{see also|Double truth}}

Thomas Aquinas believed "that for the knowledge of any truth whatsoever man needs divine help, that the intellect may be moved by God to its act."<ref>{{cite web |url=http://saints.sqpn.com/saint-thomas-aquinas/ |title=Blog Archive " Saint Thomas Aquinas |date=22 October 1974 |publisher=Saints.SQPN.com |access-date=17 January 2010}}</ref> However, he believed that human beings have the natural capacity to know many things without special [[divine revelation]], even though such revelation occurs from time to time, "especially in regard to such (truths) as pertain to faith."<ref name="Summa I-II Q109a1">{{cite web |url= http://ccel.org/ccel/aquinas/summa.FS_Q109_A1.html#FS_Q109_A1-p9 |title=''Summa'', I–II, Q109a1 |via =ccel.org |access-date=25 March 2012}}</ref> But this is the light that is given to man by God according to man's nature: "Now every form bestowed on created things by God has power for a determined act[uality], which it can bring about in proportion to its own proper endowment; and beyond which it is powerless, except by a superadded form, as water can only heat when heated by the fire. And thus the human understanding has a form, viz. intelligible light, which of itself is sufficient for knowing certain intelligible things, viz. those we can come to know through the senses."<ref name="Summa I-II Q109a1" />

===Ethics===
{{see also|Christian ethics}}
{{Redirect|Eternal law|2012 fantasy drama series|Eternal Law}}
Thomas was aware that the Albigensians and the Waldensians challenged moral precepts concerning marriage and ownership of private property and that challenges could ultimately be resolved only by logical arguments based on self-evident norms. He accordingly argued, in the Summa Theologiae, that just as the [[first principle]] of demonstration is the self-evident principle of noncontradiction ("the same thing cannot be affirmed and denied at the same time"), the first principle of action is the self-evident ''Bonum'' precept ("good is to be done and pursued and evil avoided").<ref>{{Cite book |last=Aquinas |first=Thomas |title=Summa Theologica, I-II q. 94, a. 2c |publisher= |url=https://www.newadvent.org/summa/2094.htm}}</ref>

This natural law precept prescribes doing and pursuing what reason knows is good while avoiding evil. Reason knows what is objectively good because good is naturally beneficial and evil is the contrary. To explain goods that are naturally self-evident, Thomas divides them into three categories: substantial goods of self-preservation desired by all; the goods common to both animals and humans, such as procreation and education of offspring; and goods characteristic of rational and intellectual beings, such as living in community and pursuing the truth about God.<ref>{{Cite book |last=Aquinas |first=Thomas |title=Summa Theologica I-II q. 94, a. 2.}}</ref>

To will such natural goods to oneself and to others is to love. Accordingly, Thomas states that the love precept obligating loving God and neighbour are "the first general principles of the natural law, and are self-evident to human reason, either through nature or through faith. Wherefore all the precepts of the decalogue are referred to these, as conclusions to general principles."<ref>{{Cite book |last=Aquinas |first=Thomas |title=Summa Theologica I-II q. 100, a. 3 ad 1.}}</ref><ref>{{Cite journal |last=Lemmons |first=R. Mary Hayden |date=1992 |title="Are the Love Precepts Really Natural Law's Primary Precepts?" |url=https://www.pdcnet.org/acpaproc/Proceedings-of-the-American-Catholic-Philosophical-Association |journal=Proceedings of the American Catholic Philosophical Association |volume=LXVI |pages=45–71 |doi=10.5840/acpaproc1992661 |via=Philosophy Documentation Center}}</ref>

To so focus on lovingly willing good is to focus natural law on acting virtuously. In his ''Summa Theologiae'', Thomas wrote:

{{blockquote|Virtue denotes a certain perfection of a power. Now a thing's perfection is considered chiefly in regard to its end. But the end of power is act. Wherefore power is said to be perfect, according as it is determinate to its act.<ref>{{Cite book |chapter-url= http://ccel.org/ccel/aquinas/summa.FS_Q55_A1.html#FS_Q55_A1-p8 | author= Thomas Aquinas| title= Summa Theologica | chapter= Question 55, Reply 1 |via= ccel.org |access-date=2012-02-02}}</ref>}}

Thomas emphasized that "[[Synderesis]] is said to be the law of our mind, because it is a habit containing the precepts of the natural law, which are the first principles of human actions."<ref name=SEP4 /><ref>{{cite book| author= Thomas Aquinas| title= Summa Theologica| volume= First Part of the Second Part| chapter= Question 94, Reply Obj. 2}}</ref>

According to Thomas "...{{nbsp}}all acts of virtue are prescribed by the natural law: since each one's reason naturally dictates to him to act virtuously. But if we speak of virtuous acts, considered in themselves, i.e., in their proper species, thus not all virtuous acts are prescribed by the natural law: for many things are done virtuously, to which nature does not incline at first; but that, through the inquiry of reason, have been found by men to be conducive to well living." Therefore, we must determine if we are speaking of virtuous acts as under the aspect of virtuous or as an act in its species.<ref name="Thomas Aquinas">{{cite book| author= Thomas Aquinas| title= Summa Theologica | chapter= Question 94, Article 3}}</ref>

Thomas defined the four [[cardinal virtues]] as [[prudence]], [[temperance (virtue)|temperance]], [[justice]], and [[courage|fortitude]]. The cardinal virtues are natural and revealed in nature, and they are binding on everyone. There are, however, three [[theological virtues]]: [[faith]], [[hope]], and [[charity (virtue)|charity]]. Thomas also describes the virtues as imperfect (incomplete) and perfect (complete) virtues. A perfect virtue is any virtue with charity, charity completes a cardinal virtue. A non-Christian can display courage, but it would be courage with temperance. A Christian would display courage with charity. These are somewhat supernatural and are distinct from other virtues in their object, namely, God:

{{blockquote|Now the object of the theological virtues is God Himself, Who is the last end of all, as surpassing the knowledge of our reason. On the other hand, the object of the intellectual and moral virtues is something comprehensible to human reason. Therefore the theological virtues are specifically distinct from the moral and intellectual virtues.<ref>{{cite book| author= Thomas Aquinas| title= Summa Theologica | chapter= Question 62, Article 2| chapter-url=http://ccel.org/ccel/aquinas/summa.FS_Q62_A2.html#FS_Q62_A2-p6 | via= ccel.org |access-date=2012-02-02}}</ref>}}

Thomas Aquinas wrote "[Greed] is a sin against God, just as all mortal sins, in as much as man condemns things eternal for the sake of temporal things."<ref>{{cite book| author= Thomas Aquinas| title= Summa Theologica | volume= Second Part of the Second Part| chapter= Question 118, Article 1 |chapter-url= http://www.ccel.org/a/aquinas/summa/SS/SS118.html#SSQ118A1THEP1 |via= ccel.org| access-date= 26 October 2018}}</ref>

Furthermore, in his ''[[Treatise on Law]]'', Thomas distinguished four kinds of law: eternal, [[Natural law|natural]], human, and [[Divine law|divine]]. ''Eternal law'' is the decree of God that governs all creation: "That Law which is the Supreme Reason cannot be understood to be otherwise than unchangeable and eternal."<ref>{{cite book| author= Thomas Aquinas| title= Summa Theologica | chapter= Question 91, Article 1}}</ref> ''Natural law'' is the human "participation" in the ''eternal law'' and is discovered by [[reason]].<ref>{{Cite book |url=https://archive.org/details/ethics00loui |title=Ethics: Discovering Right and Wrong |last=Pojman |first=Louis |publisher=Wadsworth Publishing Company |year=1995 |isbn=0-534-56138-1 |location=Belmont, California |author-link=Louis Pojman}}</ref> ''Natural law'' is based on "[[first principles]]":

{{blockquote|. . . this is the first precept of the law, that good is to be done and promoted, and evil is to be avoided. All other precepts of the natural law are based on this . . .<ref>{{Cite book |chapter-url= http://ccel.org/ccel/aquinas/summa.FS_Q94_A2.html#FS_Q94_A2-p7 | author= Thomas Aquinas| title= Summa Theologica | chapter= Question 94, Article 2 |via= ccel.org |access-date=2012-02-02}}</ref>}}

Whether the natural law contains several precepts, or one only is explained by Thomas, "All the inclinations of any parts whatsoever of human nature, e.g., of the concupiscible and irascible parts, in so far as they are ruled by reason, belong to the natural law, and are reduced to one first precept, as stated above: so that the precepts of the natural law are many in themselves, but are based on one common foundation."<ref>{{cite book| author= Thomas Aquinas| title= Summa Theologica | chapter= Question 94, Second Article, Reply Obj. 2}}</ref>

[[File:Tommaso Aquino - Francisco de Zurbarán.jpg|thumb|upright=.7|Detail of ''[[The Apotheosis of Saint Thomas Aquinas]]'' by [[Francisco de Zurbarán]], 1631]]
The desires to live and to procreate are counted by Thomas among those basic (natural) human values on which all human values are based. According to Thomas, all human tendencies are geared towards real human goods. In this case, the human nature in question is marriage, the total gift of oneself to another that ensures a family for children and a future for mankind.<ref>{{Cite book |chapter-url= http://www.corpusthomisticum.org/snp4027.html |volume= IV, Commentary| title=In Sententiae |chapter= d. 27 q. 1 a.1 |last=Aquinas |first=Thomas |via= corpusthomisticum.org |access-date=21 September 2011}}</ref> He defined the dual inclination of the action of love: "towards the good which a man wishes to someone (to himself or to another) and towards that to which he wishes some good".<ref name="newadvent.org">{{Cite book |chapter-url=http://www.newadvent.org/summa/2026.htm#article4 | author= Thomas Aquinas| title= Summa Theologica | chapter= STh I–II, 26, 4, corp. art |via= New Advent |access-date=30 October 2010}}</ref>

Concerning Human Law, Thomas concludes, "...{{nbsp}}that just as, in the speculative reason, from naturally known indemonstrable principles, we draw the conclusions of the various sciences, the knowledge of which is not imparted to us by nature, but acquired by the efforts of reason, so to it is from the precepts of the natural law, as from general and indemonstrable principles, that human reason needs to proceed to the more particular determination of certain matters. These particular determinations, devised by human reason, are called human laws, provided the other essential conditions of law be observed{{nbsp}}..." Human law is [[positive law]]: the natural law applied by governments to societies.<ref name="Thomas Aquinas"/>

Natural and human law is not adequate alone. The need for human behaviour to be directed made it necessary to have Divine law. Divine law is the specially revealed law in the [[scriptures]]. Thomas quotes, "The Apostle says (Hebrews 7.12): The priesthood being translated, it is necessary that a translation also be made of the law. But the priesthood is twofold, as stated in the same passage, viz, the levitical priesthood, and the priesthood of Christ. Therefore, the Divine law is twofold, namely, the Old Law and the New Law."<ref>{{cite book| author= Thomas Aquinas| title= Summa Theologica | chapter= Question 94, Article 5}}</ref>

Thomas also greatly influenced Catholic understandings of [[mortal sin|mortal]] and [[venial sin]]s.

Thomas Aquinas refers to animals as dumb and that the natural order has declared animals for man's use. Thomas denied that human beings have any duty of charity to animals because they are not persons. Otherwise, it would be unlawful to kill them for food. But humans should still be charitable to them, for "cruel habits might carry over into our treatment of human beings."<ref>{{Cite book |title=The Oxford Companion to Philosophy |year=1995 |editor-last=Honderich |editor-first=Ted |location=Oxford |pages=35–36 |chapter=Animals: Peter Singer |chapter-url=http://www.utilitarian.net/singer/by/1995----04.htm | via= utilitarian.net }}</ref><ref>{{cite book| author= Thomas Aquinas| title= Summa Theologica | volume= Second Part of the Second Part| chapter= Question 64. Article 1}}</ref>

Thomas contributed to [[History of economic thought#Economic thought in the Middle Ages (500–1500 AD)|economic thought]] as an aspect of ethics and justice. He dealt with the concept of a [[just price]], normally its market price or a regulated price sufficient to cover seller [[costs of production]]. He argued it was immoral for sellers to raise their prices simply because buyers were in pressing need of a product.<ref>{{cite book| author= Thomas Aquinas| title= Summa Theologica | chapter-url= http://www.saylor.org/site/wp-content/uploads/2012/06/ECON301-2.1.2-1st.pdf |chapter= Of Cheating, Which Is Committed in Buying and Selling| translator= The Fathers of the English Dominican Province| access-date= 19 June 2012}}</ref><ref>{{Cite book |title=The New Palgrave: A Dictionary of Economics |title-link=The New Palgrave: A Dictionary of Economics |last=Gordon |first=Barry |year=2009 |volume=1 |chapter=Aquinas, St Thomas (1225–1274) |orig-year=1987 |page=100}}</ref>

===Political order===
Thomas's theory of political order became highly influential. He sees man as a social being who lives in a community and interacts with its other members. That leads, among other things, to the [[division of labour]].

Thomas made a distinction between a good man and a good citizen, which was important to the development of [[libertarian]] theory. That indicates, in the eyes of the atheist libertarian writer [[George H. Smith]], that the sphere of [[individual autonomy]] was one which the state could not interfere with.{{sfn|Smith |2008|p=18}}

Thomas thought that monarchy was the best form of government because a monarch does not have to form compromises with other persons. Thomas, however, held that monarchy in only a very specific sense was the best form of government—only when the king was virtuous is it the best form; otherwise if the monarch is vicious it is the worst kind (see De Regno I, Ch. 2). Moreover, according to Thomas, [[oligarchy]] degenerates more easily into [[tyranny]] than monarchy. To prevent a king from becoming a tyrant, his political powers must be curbed. Unless an agreement of all persons involved can be reached, a tyrant must be tolerated, as otherwise, the political situation could deteriorate into anarchy, which would be even worse than tyranny. In his political work ''[[List of works by Thomas Aquinas#De Regno, to the King of Cyprus|De Regno]]'', Thomas subordinated the political power of the king to the primacy of the divine and human law of [[Creator deity#Christianity|God the creator]]. For example, he affirmed:
{{blockquote|Just as the government of a king is the best, so the government of a tyrant is the worst.|{{cite web|url=https://isidore.co/aquinas/DeRegno.htm#4|title=''De Regno'', Ch. 4, n. 21|language=Latin, English}}}}
{{blockquote|It is plain, therefore, from what has been said, that a king is one who rules the people of one city or province, and rules them for the common good.|{{cite web|url=https://isidore.co/aquinas/DeRegno.htm#2|title=''De Regno'', Ch. 2, n. 15|language=Latin, English}}}}

According to Thomas, monarchs are God's representatives in their territories, but the church, represented by the popes, is above the kings in matters of doctrine and ethics. As a consequence, worldly rulers are obliged to adapt their laws to the Catholic Church's doctrines and determinations.

Thomas said slavery was not the natural state of man.<ref>Weithman, Paul J. (1992). [https://www3.nd.edu/~pweithma/My%20Papers/Augustine%20and%20Aquinas%20on%20Political%20Authority.pdf "Augustine and Aquinas on Original Sin and the Function of Political Authority"] {{Webarchive|url=https://web.archive.org/web/20211209001913/https://www3.nd.edu/~pweithma/My%20Papers/Augustine%20and%20Aquinas%20on%20Political%20Authority.pdf |date=9 December 2021 }}, p. 356.</ref> He also held that a slave is by nature equal to his master (''Summa Theologiae Supplement'', Q52, A2, ad 1). He distinguished between 'natural slavery', which is for the benefit of both master and slave, and 'servile slavery', which removes all autonomy from the slave and is, according to Thomas, worse than death.<ref>{{cite web |url=http://ldysinger.stjohnsem.edu/@texts2/1271_aquinas/08_aq_slavery-ST3.htm |title=Aquinas on Slavery |website= stjohnsem.edu |access-date=26 November 2019}}</ref>
Aquinas' doctrines of the Fair Price,<ref>{{cite journal|author1=Nureev Rustem, M.|title=Doctrine of "Fair Price" by Thomas Aquinas: background, laws of development and specific interpretation|journal=Journal of Institutional Studies|issue=1|volume=7|date=1 March 2015|pages=6–24|doi=10.17835/2076-6297.2015.7.1.006-024|issn= 2076-6297|oclc= 8773558345|doi-access=free}}</ref> of the right of [[tyrannicide]] and of the equality of all the baptized sons of God in the [[Communion of saints]] established a limit to the political power to prevent it from degenerating into tyranny. This system had a concern in the Protestant opposition to the Roman Catholic Church and in "disinterested" replies to Thomism carried out by [[Immanuel Kant|Kant]] and by [[Baruch Spinoza|Spinoza]].

==== Death penalty ====
In [[Summa Contra Gentiles]], Book 3, Chapter 146, which was written by Thomas prior to writing the [[Summa Theologica]], Thomas allowed the judicial death penalty. He stated:<ref>Summa Conta Gentiles, Book III, Chapter 146, paragraphs 2–5 https://isidore.co/aquinas/ContraGentiles3b.htm#146 {{Webarchive|url=https://web.archive.org/web/20221030102342/https://isidore.co/aquinas/ContraGentiles3b.htm#146 |date=30 October 2022 }}</ref>

{{Blockquote|[M]en who are in authority over others do no wrong when they reward the good and punish the evil.

[…] for the preservation of concord among men it is necessary that punishments be inflicted on the wicked. Therefore, to punish the wicked is not in itself evil.

Moreover, the common good is better than the particular good of one person. So, the particular good should be removed in order to preserve the common good. But the life of certain pestiferous men is an impediment to the common good which is the concord of human society. Therefore, certain men must be removed by death from the society of men.

Furthermore, just as a physician looks to health as the end in his work, and health consists in the orderly concord of humors, so, too, the ruler of a state intends peace in his work, and peace consists in "the ordered concord of citizens." Now, the physician quite properly and beneficially cuts off a diseased organ if the corruption of the body is threatened because of it. Therefore, the ruler of a state executes pestiferous men justly and sinlessly in order that the peace of the state may not be disrupted.}}

However, in the same discussion:
{{Blockquote| The unjust execution of men is prohibited…Killing which results from anger is prohibited…The execution of the wicked is forbidden wherever cannot be done without danger to the good. }}

===Just war===
{{See also|Just War}}

While it would be contradictory to speak of a "just schism", a "just brawling" or a "just sedition", the word "war" permits sub-classification into good and bad kinds. Thomas Aquinas, centuries after [[Augustine of Hippo]], used the authority of Augustine's arguments in an attempt to define the conditions under which a war could be just.<ref>{{Cite web |title=The Just War |url=http://www.catholiceducation.org/articles/politics/pg0029.html |url-status=live |archive-url=https://web.archive.org/web/20210423100800/https://www.catholiceducation.org/articles/politics/pg0029.html |archive-date=23 April 2021 |access-date=24 February 2012}}</ref> He laid these out in his work ''[[Summa Theologica]]'':
* First, war must occur for a good and just purpose rather than the pursuit of wealth or power.
* Second, just war must be waged by a properly instituted authority such as the state.
* Third, peace must be a central motive even in the midst of violence.<ref>{{Cite book |last=Gonzalez |first=Justo L. |url=https://archive.org/details/storyofchristian01gonz |title=The Story of Christianity |publisher=HarperSanFrancisco |year=1984 |url-access=registration}}</ref>

===Psychology and anthropology===
Thomas Aquinas maintains that a human is a single material substance. He understands the soul as the form of the body, which makes a human being the composite of the two. Thus, only living, form-matter composites can truly be called human; dead bodies are "human" only analogously. One actually existing substance comes from body and soul. A human is a single material substance, but still should be understood as having an immaterial soul, which continues after bodily death.

In his ''Summa Theologiae'' Thomas states his position on the nature of the soul; defining it as "the first principle of life".<ref>{{Cite book |title=Summa Theologiae of St. Thomas Aquinas |last=Aquinas |first=Thomas |year=1920 |edition=Second and Revised |translator-last=The Fathers of the English Dominican Province |chapter=Question 75, Article 1}}</ref> The soul is not corporeal, or a body; it is the act of a body. Because the intellect is incorporeal, it does not use the bodily organs, as "the operation of anything follows the mode of its being".<ref>{{Cite book |title=Summa Theologiae of St. Thomas Aquinas |last=Aquinas |first=Thomas |year=1920 |edition=Second and Revised |translator-last=The Fathers of the English Dominican Province |chapter=Question 75, Article 3}}</ref>

[[File:Luis muñoz-santo tomás de aquino.jpg|thumb|right|Saint Thomas Aquinas by Luis Muñoz Lafuente]]
According to Thomas, the soul is not matter, not even incorporeal or spiritual matter. If it were, it would not be able to understand universals, which are immaterial. A receiver receives things according to the receiver's own nature, so for the soul (receiver) to understand (receive) universals, it must have the same nature as universals. Yet, any substance that understands universals may not be a matter-form composite. So, humans have rational souls, which are abstract forms independent of the body. But a human being is one existing, single material substance that comes from body and soul: that is what Thomas means when he writes that "something one in nature can be formed from an intellectual substance and a body", and "a thing one in nature does not result from two permanent entities unless one has the character of substantial form and the other of matter."<ref>{{Cite book |title=Summa Contra Gentiles |last=Aquinas |first=Thomas |publisher=U. of Notre Dame Press |year=1975 |location=Notre Dame, Ind. |translator-last=Anton C. Pegis |chapter=5 volumes. |display-authors=etal}}</ref>

===Economics===
Thomas Aquinas addressed most economic questions within the framework of justice, which he contended was the highest of the moral virtues.<ref>{{Cite web |url=https://www.newadvent.org/summa/2066.htm#article4 |title=''Summa Theologica'', Question 64, Article 4, "Whether justice is the chief of the moral virtues?" |access-date=29 May 2020 |archive-date=19 April 2021 |archive-url=https://web.archive.org/web/20210419033704/https://www.newadvent.org/summa/2066.htm#article4 |url-status=live }}</ref> He says that justice is "a habit whereby man renders to each his due by a constant and perpetual will."<ref>{{Cite book |title=Summa Theologica |last=Aquinas |first=Thomas |publisher=English Dominican Fathers |year=1981 |location=New York |pages=II-II, Q58, A1}}</ref> He argued that this concept of justice has its roots in natural law. Joseph Schumpeter, in his ''History of Economic Analysis'', concluded that "All the economic questions put together matters less to him than did the smallest point of theological or philosophical doctrine, and it is only where economic phenomena raise questions of moral theology that he touches upon them at all."<ref>{{Cite book |title=History of Economic Analysis |last=Schumpeter |first=Joseph |publisher=Oxford University Press |year=1954 |location=New York |page=90}}</ref>

Modern Western views concerning [[capitalism]], [[unfair labor practice]], [[living wage]], [[price gouging]], monopolies, fair trade practices, and [[predatory pricing]], inter alia, are remnants of the inculcation of Aquinas' interpretation of natural moral law.<ref>Colish, Marcia, ''Medieval Foundations of the Western Intellectual Tradition, 400–1400'', Yale University Press, 1997, pp. 333–334</ref>

====Just price====
Thomas Aquinas distinguished the [[Just price|just]], or natural, price of a good from that price which manipulates another party. He determines the just price from a number of things. First, the just price must be relative to the worth of the good. Thomas held that the price of a good measures its quality: "the quality of a thing that comes into human use is measured by the price given for it".<ref>{{Cite book |title=Summa Theologica |last=Aquinas |first=Thomas |publisher=English Dominican Fathers |year=1981 |location=New York |pages=II-II, Q77, A1}}</ref> The price of a good, measured by its worth, is determined by its usefulness to man. This worth is subjective because each good has a different level of usefulness to every man. The price should reflect the current value of a good according to its usefulness to man. "Gold and silver are costly not only on account of the usefulness of the vessels and other like things made from them, but also on account of the excellence and purity of their substance."<ref>{{Cite book |title=Summa Theologica |last=Aquinas |first=Thomas |publisher=English Dominican Fathers |year=1981 |location=New York |pages=II-II, Q77, A2}}</ref>

==== Social justice ====
{{Integralism |expanded=people}}
Thomas defines [[distributive justice]] as follows:<ref>{{Cite web |title=Summa Theologiae: The parts of Justice (Secunda Secundae Partis, Q. 61) |url=https://www.newadvent.org/summa/3061.htm |access-date=30 August 2022 |website=www.newadvent.org}}</ref><blockquote>[I]n distributive justice something is given to a private individual, in so far as what belongs to the whole is due to the part, and in a quantity that is proportionate to the importance of the position of that part in respect of the whole. Consequently, in distributive justice a person receives all the more of the common goods, according as he holds a more prominent position in the community. This prominence in an aristocratic community is gauged according to virtue, in an oligarchy according to wealth, in a democracy according to liberty, and in various ways according to various forms of community. Hence in distributive justice the mean is observed, not according to equality between thing and thing, but according to proportion between things and persons: in such a way that even as one person surpasses another, so that which is given to one person surpasses that which is allotted to another.</blockquote>Thomas asserts that Christians have a duty to distribute with provision to the poorest of society.<ref>Gilson, Etienne, ''The Christian Philosophy of St. Thomas Aquinas'', University of Notre Dame Press, 1994</ref>

"[[Social justice]]" is a term that arose in the 19th century in the writings of Luigi Taparelli,<ref>{{Cite web |date=8 October 2014 |title=The Origins of Social Justice: Taparelli d'Azeglio |url=https://isi.org/intercollegiate-review/the-origins-of-social-justice-taparelli-dazeglio/}}</ref> and it was his term for the reality Thomas Aquinas called "legal justice" or "general justice". Legal or social justice is the contribution of the individual to the common good. So for Thomas, distributive justice goes in the direction from the [[common good]] to the individual, and is a proportional distribution of common goods, to individuals based on their contribution to the community. Legal or general justice, or what came to be called social justice, goes in the other direction, from the individuals to the common good.<ref>{{Cite web|url=https://aquinas.cc/la/en/~Eth.Bk5|title=Aquinas|website=aquinas.cc}}</ref>

It is helpful to understand as well other related types of justice: if social justice is from the individual to the community, and distributive justice is from the community to the individual, there is also commutative justice (between two individuals, as in buying and selling, or stealing and returning) as well as retributive justice (rectifications that occur to restore justice, once justice has been violated).<ref>{{Cite web|url=https://aquinas.cc/la/en/~ST.II-II.Q61|title=Aquinas|website=aquinas.cc}}</ref><ref>{{Cite web|url=https://www.newadvent.org/summa/3061.htm|title=SUMMA THEOLOGIAE: The parts of Justice (Secunda Secundae Partis, Q. 61)|website=www.newadvent.org}}</ref>

==== Usury ====
The [[Second Lateran Council]] called the practice of loaning money "detestable and shameful... insatiable rapacity of money lenders, forbidden both by divine and human laws throughout the Old and New Testament, we condemn, and separate from the ecclesiastical consolation".<ref>{{Cite web |title=Denzinger EN 712 |url=http://www.clerus.org/bibliaclerusonline/en/dwy.htm |access-date=30 August 2022 |website=www.clerus.org}}</ref> The [[Fifth Lateran Council]] defined [[usury]] as "when, from its use, a thing which produces nothing is applied to the acquiring of gain and profit without any work, any expense or any risk".<ref>{{Cite web |title=The Red Herring of Usury |url=https://www.catholic.com/magazine/print-edition/the-red-herring-of-usury |access-date=30 August 2022 |website=Catholic Answers}}</ref>

Thomas Aquinas also wrote extensively on [[usury]], that is, the lending of money with interest. He condemned its practice: "to take usury for money lent is unjust in itself, because this is to sell what does not exist, and this evidently leads to inequality which is contrary to justice".<ref>{{Cite book |title=Summa Theologica |author=Thomas Aquinas |publisher=English Dominican Fathers |year=1981 |location=New York |pages=II-II, Q78, A1}}</ref> Money, and other similar goods, are consumed only when they are used. Charging a premium for money lent is a charge for ''more'' than the use of the good. Thus, Thomas Aquinas concluded that the lender is charging for something not his own, in other words, not rendering to each his due.