Reply Obj. 2: The affirmative precepts are distinct from the negative, when one is not comprised in the other: thus that man should honor his parents does not include that he should not kill another man; nor does the latter include the former. But when an affirmative precept is included in a negative, or vice versa, we do not find that two distinct precepts are given: thus there is not one precept saying that "Thou shalt not steal," and another binding one to keep another's property intact, or to give it back to its owner. In the same way there are not different precepts about believing in God, and about not believing in strange gods.
Reply Obj. 3: All covetousness has one common ratio: and therefore the Apostle speaks of the commandment about covetousness as though it were one. But because there are various special kinds of covetousness, therefore Augustine distinguishes different prohibitions against coveting: for covetousness differs specifically in respect of the diversity of actions or things coveted, as the Philosopher says (Ethic. x, 5). ________________________
FIFTH ARTICLE [I-II, Q. 100, Art. 5]
Whether the Precepts of the Decalogue Are Suitably Set Forth?
Objection 1: It would seem that the precepts of the decalogue are unsuitably set forth. Because sin, as stated by Ambrose (De Paradiso viii), is "a transgression of the Divine law and a disobedience to the commandments of heaven." But sins are distinguished according as man sins against God, or his neighbor, or himself. Since, then, the decalogue does not include any precepts directing man in his relations to himself, but only such as direct him in his relations to God and himself, it seems that the precepts of the decalogue are insufficiently enumerated.
Obj. 2: Further, just as the Sabbath-day observance pertained to the worship of God, so also did the observance of other solemnities, and the offering of sacrifices. But the decalogue contains a precept about the Sabbath-day observance. Therefore it should contain others also, pertaining to the other solemnities, and to the sacrificial rite.
Obj. 3: Further, as sins against God include the sin of perjury, so also do they include blasphemy, or other ways of lying against the teaching of God. But there is a precept forbidding perjury, "Thou shalt not take the name of the Lord thy God in vain." Therefore there should be also a precept of the decalogue forbidding blasphemy and false doctrine.
Obj. 4: Further, just as man has a natural affection for his parents, so has he also for his children. Moreover the commandment of charity extends to all our neighbors. Now the precepts of the decalogue are ordained unto charity, according to 1 Tim. 1:5: "The end of the commandment is charity." Therefore as there is a precept referring to parents, so should there have been some precepts referring to children and other neighbors.
Obj. 5: Further, in every kind of sin, it is possible to sin in thought or in deed. But in some kinds of sin, namely in theft and adultery, the prohibition of sins of deed, when it is said, "Thou shalt not commit adultery, Thou shalt not steal," is distinct from the prohibition of the sin of thought, when it is said, "Thou shalt not covet thy neighbor's goods," and, "Thou shalt not covet thy neighbor's wife." Therefore the same should have been done in regard to the sins of homicide and false witness.
Obj. 6: Further, just as sin happens through disorder of the concupiscible faculty, so does it arise through disorder of the irascible part. But some precepts forbid inordinate concupiscence, when it is said, "Thou shalt not covet." Therefore the decalogue should have included some precepts forbidding the disorders of the irascible faculty. Therefore it seems that the ten precepts of the decalogue are unfittingly enumerated.