Thomas Aquinas

“ It belongs to justice to render to each one his right, the distinction between individuals being presupposed: for if a man gives himself his due, this is not strictly called "just." And since what belongs to the son is his father's, and what belongs to the slave is his master's, it follows that properly speaking there is not justice of father to son, or of master to slave. ”

“ The Divine right is that which is promulgated by God. Such things are partly those that are naturally just, yet their justice is hidden to man, and partly are made just by God's decree. Hence also Divine right may be divided in respect of these two things, even as human right is. For the Divine law commands certain things because they are good, and forbids others, because they are evil, while others are good because they are prescribed, and others evil because they are forbidden. ”

“ Since justice implies equality, and since we cannot offer God an equal return, it follows that we cannot make Him a perfectly just repayment. For this reason the Divine law is not properly called "jus" but "fas," because, to wit, God is satisfied if we accomplish what we can. Nevertheless justice tends to make man repay God as much as he can, by subjecting his mind to Him entirely.
Art. 2 - Whether right is fittingly divided into natural right and positive right? Objection 1: It would seem that right is not fittingly divided into natural right and positive right. ”

“ A son, as such, belongs to his father, and a slave, as such, belongs to his master; yet each, considered as a man, is something having separate existence and distinct from others. Hence in so far as each of them is a man, there is justice towards them in a way: and for this reason too there are certain laws regulating the relations of father to his son, and of a master to his slave ”

“ Accordingly that which is right in the works of the other virtues, and to which the intention of the virtue tends as to its proper object, depends on its relation to the agent only, whereas the right in a work of justice, besides its relation to the agent, is set up by its relation to others. ”

“ That which is natural to one whose nature is unchangeable, must needs be such always and everywhere. But man's nature is changeable, wherefore that which is natural to man may sometimes fail. Thus the restitution of a deposit to the depositor is in accordance with natural equality, and if human nature were always right, this would always have to be observed ”

“ For this reason justice has its own special proper object over and above the other virtues, and this object is called the just, which is the same as "right." Hence it is evident that right is the object of justice. ”

“ Further, Divine right is not natural right, since it transcends human nature. In like manner, neither is it positive right, since it is based not on human, but on Divine authority. Therefore right is unfittingly divided into natural and positive. ”

“ Now it belongs not only to man but also to other animals to apprehend a thing absolutely: wherefore the right which we call natural, is common to us and other animals according to the first kind of commensuration. But the right of nations falls short of natural right in this sense, as the jurist [*Digest. i, 1; De Just. et Jure i] says because "the latter is common to all animals, while the former is common to men only." ”

“ For that which is natural is unchangeable, and is the same for all. Now nothing of the kind is to be found in human affairs, since all the rules of human right fail in certain cases, nor do they obtain force everywhere. Therefore there is no such thing as natural right.
Objection 2: Further, a thing is called "positive" when it proceeds from the human will. But a thing is not just, simply because it proceeds from the human will, else a man's will could not be unjust. ”

“ Secondly a thing is naturally commensurate with another person, not according as it is considered absolutely, but according to something resultant from it, for instance the possession of property. For if a particular piece of land be considered absolutely, it contains no reason why it should belong to one man more than to another, but if it be considered in respect of its adaptability to cultivation, and the unmolested use of the land, it has a certain commensuration to be the property of one and not of another man, as the Philosopher shows (Polit. ii, 2) . ”

“ Hence a father is not compared to his son as to another simply, and so between them there is not the just simply, but a kind of just, called "paternal." In like manner neither is there the just simply, between master and servant, but that which is called "dominative." ”

“ Just as there pre-exists in the mind of the craftsman an expression of the things to be made externally by his craft, which expression is called the rule of his craft, so too there pre-exists in the mind an expression of the particular just work which the reason determines, and which is a kind of rule of prudence. ”

“ Secondly a thing is said to be other from something else, not simply, but as belonging in some way to that something else: and in this way, as regards human affairs, a son belongs to his father, since he is part of him somewhat, as stated in Ethic. viii, 12, and a slave belongs to his master, because he is his instrument, as stated in Polit. ”