Objection 1. It would seem that it is impossible to assign a distinct division of the judicial precepts. Because the judicial precepts direct men in their relations to one another. But those things which need to be directed, as pertaining to the relationship between man and man, and which are made use of by men, are not subject to division, since they are infinite in number. Therefore it is not possible to assign a distinct division of the judicial precepts.
Objection 2. Further, the judicial precepts are decisions on moral matters. But moral precepts do not seem to be capable of division, except in so far as they are reducible to the precepts of the decalogue. Therefore there is no distinct division of the judicial precepts.
Objection 3. Further, because there is a distinct division of the ceremonial precepts, the Law alludes to this division, by describing some as "sacrifices," others as "observances." But the Law contains no allusion to a division of the judicial precepts. Therefore it seems that they have no distinct division.
On the contrary, Wherever there is order there must needs be division. But the notion of order is chiefly applicable to the judicial precepts, since thereby that people was ordained. Therefore it is most necessary that they should have a distinct division.
I answer that, Since law is the art, as it were, of directing or ordering the life of man, as in every art there is a distinct division in the rules of art, so, in every law, there must be a distinct division of precepts: else the law would be rendered useless by confusion. We must therefore say that the judicial precepts of the Old Law, whereby men were directed in their relations to one another, are subject to division according to the divers ways in which man is directed.
Now in every people a fourfold order is to be found: one, of the people's sovereign to his subjects; a second of the subjects among themselves; a third, of the citizens to foreigners; a fourth, of members of the same household, such as the order of the father to his son; of the wife to her husband; of the master to his servant: and according to these four orders we may distinguish different kinds of judicial precepts in the Old Law. For certain precepts are laid down concerning the institution of the sovereign and relating to his office, and about the respect due to him: this is one part of the judicial precepts. Again, certain precepts are given in respect of a man to his fellow citizens: for instance, about buying and selling, judgments and penalties: this is the second part of the judicial precepts. Again, certain precepts are enjoined with regard to foreigners: for instance, about wars waged against their foes, and about the way to receive travelers and strangers: this is the third part of the judicial precepts. Lastly, certain precepts are given relating to home life: for instance, about servants, wives and children: this is the fourth part of the judicial precepts.
Reply to Objection 1. Things pertaining to the ordering of relations between one man and another are indeed infinite in number: yet they are reducible to certain distinct heads, according to the different relations in which one man stands to another, as stated above.
Reply to Objection 2. The precepts of the decalogue held the first place in the moral order, as stated above (Question 100, Article 3): and consequently it is fitting that other moral precepts should be distinguished in relation to them. But the judicial and ceremonial precepts have a different binding force, derived, not from natural reason, but from their institution alone. Hence there is a distinct reason for distinguishing them.
Reply to Objection 3. The Law alludes to the division of the judicial precepts in the very things themselves which are prescribed by the judicial precepts of the Law.
Source: Summa Theologica (New Advent)