Thomas Aquinas, Summa Theologiae

Objection 1: It would seem that the mean in distributive justice is to be observed in the same way as in commutative justice. For each of these is a kind of particular justice, as stated above (Article 1). Now the mean is taken in the same way in all the parts of temperance or fortitude. Therefore the mean should also be observed in the same way in both distributive and commutative justice.

Objection 2: Further, the form of a moral virtue consists in observing the mean which is determined in accordance with reason. Since, then, one virtue has one form, it seems that the mean for both should be the same.

Objection 3: Further, in order to observe the mean in distributive justice we have to consider the various deserts of persons. Now a person's deserts are considered also in commutative justice, for instance, in punishments; thus a man who strikes a prince is punished more than one who strikes a private individual. Therefore the mean is observed in the same way in both kinds of justice.

On the contrary, The Philosopher says (Ethic. v, 3,4) that the mean in distributive justice is observed according to "geometrical proportion," whereas in commutative justice it follows "arithmetical proportion."

I answer that, As stated above (Article 1), in 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. Hence the Philosopher says (Ethic. v, 3,4) that the mean in the latter case follows "geometrical proportion," wherein equality depends not on quantity but on proportion. For example we say that 6 is to 4 as 3 is to 2, because in either case the proportion equals 1-1/2; since the greater number is the sum of the lesser plus its half: whereas the equality of excess is not one of quantity, because 6 exceeds 4 by 2, while 3 exceeds 2 by 1.

On the other hand in commutations something is paid to an individual on account of something of his that has been received, as may be seen chiefly in selling and buying, where the notion of commutation is found primarily. Hence it is necessary to equalize thing with thing, so that the one person should pay back to the other just so much as he has become richer out of that which belonged to the other. The result of this will be equality according to the "arithmetical mean" which is gauged according to equal excess in quantity. Thus 5 is the mean between 6 and 4, since it exceeds the latter and is exceeded by the former, by 1. Accordingly if, at the start, both persons have 5, and one of them receives 1 out of the other's belongings, the one that is the receiver, will have 6, and the other will be left with 4: and so there will be justice if both be brought back to the mean, 1 being taken from him that has 6, and given to him that has 4, for then both will have 5 which is the mean.

Reply to Objection 1: In the other moral virtues the rational, not the real mean, is to be followed: but justice follows the real mean; wherefore the mean, in justice, depends on the diversity of things.

Reply to Objection 2: Equality is the general form of justice, wherein distributive and commutative justice agree: but in one we find equality of geometrical proportion, whereas in the other we find equality of arithmetical proportion.

Reply to Objection 3: In actions and passions a person's station affects the quantity of a thing: for it is a greater injury to strike a prince than a private person. Hence in distributive justice a person's station is considered in itself, whereas in commutative justice it is considered in so far as it causes a diversity of things.

Articulus 2

Argumentum 1

Ad secundum sic proceditur. Videtur quod medium eodem modo accipiatur in iustitia distributiva et commutativa.

Utraque enim sub iustitia particulari continetur, ut dictum est.

Sed in omnibus temperantiae vel fortitudinis partibus accipitur uno modo medium. Ergo etiam eodem modo est accipiendum medium in iustitia distributiva et commutativa.

Argumentum 2

Praeterea, forma virtutis moralis in medio consistit quod secundum rationem determinatur. Cum ergo unius virtutis sit una forma, videtur quod in utraque sit eodem modo medium accipiendum.

Argumentum 3

Praeterea, in iustitia distributiva accipitur medium attendendo diversam dignitatem personarum. Sed dignitas personarum attenditur etiam in commutativa iustitia, sicut in punitionibus, plus enim punitur qui percussit principem quam qui percussit privatam personam. Ergo eodem modo accipitur medium in utraque iustitia.

Sed Contra

Sed contra est quod philosophus dicit, in V ethic., quod in iustitia distributiva accipitur medium secundum geometricam proportionalitatem, in commutativa autem secundum arithmeticam.

Corpus

Respondeo dicendum quod, sicut dictum est, in distributiva iustitia datur aliquid alicui privatae personae inquantum id quod est totius est debitum parti. Quod quidem tanto maius est quanto ipsa pars maiorem principalitatem habet in toto. Et ideo in distributiva iustitia tanto plus alicui de bonis communibus datur quanto illa persona maiorem principalitatem habet in communitate.

Quae quidem principalitas in aristocratica communitate attenditur secundum virtutem, in oligarchica secundum divitias, in democratica secundum libertatem, et in aliis aliter.

Et ideo in iustitia distributiva non accipitur medium secundum aequalitatem rei ad rem, sed secundum proportionem rerum ad personas, ut scilicet, sicut una persona excedit aliam, ita etiam res quae datur uni personae excedit rem quae datur alii.

Et ideo dicit philosophus quod tale medium est secundum geometricam proportionalitatem, in qua attenditur aequale non secundum quantitatem, sed secundum proportionem.

Sicut si dicamus quod sicut se habent sex ad quatuor, ita se habent tria ad duo, quia utrobique est sesquialtera proportio, in qua maius habet totum minus et mediam partem eius, non autem est aequalitas excessus secundum quantitatem, quia sex excedunt quatuor in duobus, tria vero excedunt duo in uno.

Sed in commutationibus redditur aliquid alicui singulari personae propter rem eius quae accepta est, ut maxime patet in emptione et venditione, in quibus primo invenitur ratio commutationis. Et ideo oportet adaequare rem rei, ut quanto iste plus habet quam suum sit de eo quod est alterius, tantundem restituat ei cuius est. Et sic fit aequalitas secundum arithmeticam medietatem, quae attenditur secundum parem quantitatis excessum, sicut quinque est medium inter sex et quatuor, in unitate enim excedit et exceditur. Si ergo a principio uterque habebat quinque, et unus eorum accepit unum de eo quod est alterius; unus, scilicet accipiens, habebit sex, et alii relinquentur quatuor. Erit ergo iustitia si uterque reducatur ad medium, ut accipiatur unum ab eo qui habet sex, et detur ei qui habet quatuor, sic enim uterque habebit quinque, quod est medium.

Ad 1

Ad primum ergo dicendum quod in aliis virtutibus moralibus accipitur medium secundum rationem, et non secundum rem. Sed in iustitia accipitur medium rei, et ideo secundum diversitatem rerum diversimode medium accipitur.

Ad 2

Ad secundum dicendum quod generalis forma iustitiae est aequalitas, in qua convenit iustitia distributiva cum commutativa. In una tamen invenitur aequalitas secundum proportionalitatem geometricam, in alia secundum arithmeticam.

Ad 3

Ad tertium dicendum quod in actionibus et passionibus conditio personae facit ad quantitatem rei, maior enim est iniuria si percutiatur princeps quam si percutiatur privata persona.

Et ita conditio personae in distributiva iustitia attenditur secundum se, in commutativa autem secundum quod per hoc diversificatur res.