Thomas Aquinas

“ Now it pertains to liberality to give to another of one's own, not of what is his. Therefore the act of justice does not consist in rendering to each one his own.
Objection 3: Further, it belongs to justice not only to distribute things duly, but also to repress injurious actions, such as murder, adultery and so forth. But the rendering to each one of what is his seems to belong solely to the distribution of things. Therefore the act of justice is not sufficiently described by saying that it consists in rendering to each one his own. ”

“ Although the liberal man gives of his own, yet he does so in so far as he takes into consideration the good of his own virtue, while the just man gives to another what is his, through consideration of the common good. Moreover justice is observed towards all, whereas liberality cannot extend to all. Again liberality which gives of a man's own is based on justice, whereby one renders to each man what is his. ”

“ Accordingly, this is a complete definition of justice; save that the act is mentioned instead of the habit, which takes its species from that act, because habit implies relation to act. And if anyone would reduce it to the proper form of a definition, he might say that "justice is a habit whereby a man renders to each one his due by a constant and perpetual will": and this is about the same definition as that given by the Philosopher (Ethic. v, 5) who says that "justice is a habit whereby a man is said to be capable of doing just actions in accordance with his choice." ”

“ On the other hand, the matter of justice is external operation, in so far as an operation or the thing used in that operation is duly proportionate to another person, wherefore the mean of justice consists in a certain proportion of equality between the external thing and the external person. ”

“ Thus a man may steal another's property, not through the desire to have the thing, but through the will to hurt the man; or vice versa, a man may covet another's property without wishing to steal it. Accordingly the directing of operations in so far as they tend towards external things, belongs to justice, but in so far as they arise from the passions, it belongs to the other moral virtues which are about the passions. ”

“ Hence, since justice regulates human operations, it is evident that it renders man's operations good, and, as Tully declares (De Officiis i, 7) , good men are so called chiefly from their justice, wherefore, as he says again (De Officiis i, 7) "the luster of virtue appears above all in justice."
Reply to Objection 1: When a man does what he ought, he brings no gain to the person to whom he does what he ought, but only abstains from doing him a harm. He does however profit himself, in so far as he does what he ought, spontaneously and readily, and this is to act virtuously. ”

“ Hence the mean in such like virtues is measured not by the proportion of one thing to another, but merely by comparison with the virtuous man himself, so that with them the mean is only that which is fixed by reason in our regard. ”

“ Therefore justice, being a moral virtue, is about the passions.
Objection 2: Further, justice is the means of rectifying a man's operations in relation to another man. Now such like operations cannot be rectified unless the passions be rectified, because it is owing to disorder of the passions that there is disorder in the aforesaid operations: thus sexual lust leads to adultery, and overmuch love of money leads to theft. Therefore justice must needs be about the passions. ”

“ The will may be called perpetual in two ways. First on the part of the will's act which endures for ever, and thus God's will alone is perpetual. Secondly on the part of the subject, because, to wit, a man wills to do a certain thing always. and this is a necessary condition of justice. For it does not satisfy the conditions of justice that one wish to observe justice in some particular matter for the time being, because one could scarcely find a man willing to act unjustly in every case; and it is requisite that one should have the will to observe justice at all times and in all cases. ”

“ Hence, justice properly speaking demands a distinction of supposits, and consequently is only in one man towards another. Nevertheless in one and the same man we may speak metaphorically of his various principles of action such as the reason, the irascible, and the concupiscible, as though they were so many agents: so that metaphorically in one and the same man there is said to be justice in so far as the reason commands the irascible and concupiscible, and these obey reason ”

“ Accordingly, just as charity which regards the Divine good as its proper object, is a special virtue in respect of its essence, so too legal justice is a special virtue in respect of its essence, in so far as it regards the common good as its proper object. ”

“ Such are riches and honors; and in the like it is possible to find excess, deficiency and mean, as regards men who can use them well or ill: and it is in this sense that justice is about things that are good simply. ”