On the contrary, The Apostle says ( Rom. 13:1 ): "The things that are of God, are well ordered" [Vulg.: 'Those that are, are ordained of God']. But the precepts of the decalogue were given immediately by God, as stated above (A[3]). Therefore they are arranged in becoming order.
I answer that, As stated above (AA[3],5, ad 1), the precepts of the decalogue are such as the mind of man is ready to grasp at once. Now it is evident that a thing is so much the more easily grasped by the reason, as its contrary is more grievous and repugnant to reason. Moreover, it is clear, since the order of reason begins with the end, that, for a man to be inordinately disposed towards his end, is supremely contrary to reason. Now the end of human life and society is God. Consequently it was necessary for the precepts of the decalogue, first of all, to direct man to God; since the contrary to this is most grievous. Thus also, in an army, which is ordained to the commander as to its end, it is requisite first that the soldier should be subject to the commander, and the opposite of this is most grievous; and secondly it is requisite that he should be in coordination with the other soldiers.
Now among those things whereby we are ordained to God, the first is that man should be subjected to Him faithfully, by having nothing in common with His enemies. The second is that he should show Him reverence: the third that he should offer Him service. Thus, in an army, it is a greater sin for a soldier to act treacherously and make a compact with the foe, than to be insolent to his commander: and this last is more grievous than if he be found wanting in some point of service to him.
As to the precepts that direct man in his behavior towards his neighbor, it is evident that it is more repugnant to reason, and a more grievous sin, if man does not observe the due order as to those persons to whom he is most indebted. Consequently, among those precepts that direct man in his relations to his neighbor, the first place is given to that one which regards his parents. Among the other precepts we again find the order to be according to the gravity of sin. For it is more grave and more repugnant to reason, to sin by deed than by word; and by word than by thought. And among sins of deed, murder which destroys life in one already living is more grievous than adultery, which imperils the life of the unborn child; and adultery is more grave than theft, which regards external goods.
Reply to Objection 1: Although our neighbor is better known than God by the way of the senses, nevertheless the love of God is the reason for the love of our neighbor, as shall be declared later on (SS, Q[25], A[1]; SS, Q[26], A[2]). Hence the precepts ordaining man to God demanded precedence of the others.
Reply to Objection 2: Just as God is the universal principle of being in respect of all things, so is a father a principle of being in respect of his son. Therefore the precept regarding parents was fittingly placed after the precepts regarding God. This argument holds in respect of affirmative and negative precepts about the same kind of deed: although even then it is not altogether cogent. For although in the order of execution, vices should be uprooted before virtues are sown, according to Ps. 33:15 : "Turn away from evil, and do good," and Isa. 1:16 , 17 : "Cease to do perversely; learn to do well"; yet, in the order of knowledge, virtue precedes vice, because "the crooked line is known by the straight" (De Anima i): and "by the law is the knowledge of sin" ( Rom. 3:20 ). Wherefore the affirmation precept demanded the first place. However, this is not the reason for the order, but that which is given above. Because in the precepts regarding God, which belongs to the first table, an affirmative precept is placed last, since its transgression implies a less grievous sin.
Reply to Objection 3: Although sin of thought stands first in the order of execution, yet its prohibition holds a later position in the order of reason.
Whether the precepts of the decalogue are suitably formulated?
Objection 1: It would seem that the precepts of the decalogue are unsuitably formulated. Because the affirmative precepts direct man to acts of virtue, while the negative precepts withdraw him from acts of vice. But in every matter there are virtues and vices opposed to one another. Therefore in whatever matter there is an ordinance of a precept of the decalogue, there should have been an affirmative and a negative precept. Therefore it was unfitting that affirmative precepts should be framed in some matters, and negative precepts in others.
Objection 2: Further, Isidore says (Etym. ii, 10) that every law is based on reason. But all the precepts of the decalogue belong to the Divine law. Therefore the reason should have been pointed out in each precept, and not only in the first and third.
Objection 3: Further, by observing the precepts man deserves to be rewarded by God. But the Divine promises concern the rewards of the precepts. Therefore the promise should have been included in each precept, and not only in the second and fourth.
Objection 4: Further, the Old Law is called "the law of fear," in so far as it induced men to observe the precepts, by means of the threat of punishments. But all the precepts of the decalogue belong to the Old Law. Therefore a threat of punishment should have been included in each, and not only in the first and second.
Objection 5: Further, all the commandments of God should be retained in the memory: for it is written ( Prov. 3:3 ): "Write them in the tables of thy heart." Therefore it was not fitting that mention of the memory should be made in the third commandment only. Consequently it seems that the precepts of the decalogue are unsuitably formulated.
On the contrary, It is written ( Wis. 11:21 ) that "God made all things, in measure, number and weight." Much more therefore did He observe a suitable manner in formulating His Law.
I answer that, The highest wisdom is contained in the precepts of the Divine law: wherefore it is written ( Dt. 4:6 ): "This is your wisdom and understanding in the sight of nations." Now it belongs to wisdom to arrange all things in due manner and order. Therefore it must be evident that the precepts of the Law are suitably set forth.
Reply to Objection 1: Affirmation of one thing always leads to the denial of its opposite: but the denial of one opposite does not always lead to the affirmation of the other. For it follows that if a thing is white, it is not black: but it does not follow that if it is not black, it is white: because negation extends further than affirmation. And hence too, that one ought not to do harm to another, which pertains to the negative precepts, extends to more persons, as a primary dictate of reason, than that one ought to do someone a service or kindness. Nevertheless it is a primary dictate of reason that man is a debtor in the point of rendering a service or kindness to those from whom he has received kindness, if he has not yet repaid the debt. Now there are two whose favors no man can sufficiently repay, viz. God and man's father, as stated in Ethic. viii, 14. Therefore it is that there are only two affirmative precepts; one about the honor due to parents, the other about the celebration of the Sabbath in memory of the Divine favor.
Reply to Objection 2: The reasons for the purely moral precepts are manifest; hence there was no need to add the reason. But some of the precepts include ceremonial matter, or a determination of a general moral precept; thus the first precept includes the determination, "Thou shalt not make a graven thing"; and in the third precept the Sabbath-day is fixed. Consequently there was need to state the reason in each case.
Reply to Objection 3: Generally speaking, men direct their actions to some point of utility. Consequently in those precepts in which it seemed that there would be no useful result, or that some utility might be hindered, it was necessary to add a promise of reward. And since parents are already on the way to depart from us, no benefit is expected from them: wherefore a promise of reward is added to the precept about honoring one's parents. The same applies to the precept forbidding idolatry: since thereby it seemed that men were hindered from receiving the apparent benefit which they think they can get by entering into a compact with the demons.
Reply to Objection 4: Punishments are necessary against those who are prone to evil, as stated in Ethic. x, 9. Wherefore a threat of punishment is only affixed to those precepts of the law which forbade evils to which men were prone. Now men were prone to idolatry by reason of the general custom of the nations. Likewise men are prone to perjury on account of the frequent use of oaths. Hence it is that a threat is affixed to the first two precepts.
Reply to Objection 5: The commandment about the Sabbath was made in memory of a past blessing. Wherefore special mention of the memory is made therein. Or again, the commandment about the Sabbath has a determination affixed to it that does not belong to the natural law, wherefore this precept needed a special admonition.
Whether the precepts of the decalogue are dispensable?
Objection 1: It would seem that the precepts of the decalogue are dispensable. For the precepts of the decalogue belong to the natural law. But the natural law fails in some cases and is changeable, like human nature, as the Philosopher says (Ethic. v, 7). Now the failure of law to apply in certain particular cases is a reason for dispensation, as stated above (Q[96], A[6]; Q[97], A[4]). Therefore a dispensation can be granted in the precepts of the decalogue.
Objection 2: Further, man stands in the same relation to human law as God does to Divine law. But man can dispense with the precepts of a law made by man. Therefore, since the precepts of the decalogue are ordained by God, it seems that God can dispense with them. Now our superiors are God's viceregents on earth; for the Apostle says ( 2 Cor. 2:10 ): "For what I have pardoned, if I have pardoned anything, for your sakes have I done it in the person of Christ." Therefore superiors can dispense with the precepts of the decalogue.
Objection 3: Further, among the precepts of the decalogue is one forbidding murder. But it seems that a dispensation is given by men in this precept: for instance, when according to the prescription of human law, such as evil-doers or enemies are lawfully slain. Therefore the precepts of the decalogue are dispensable.
Objection 4: Further, the observance of the Sabbath is ordained by a precept of the decalogue. But a dispensation was granted in this precept; for it is written ( 1 Macc. 2:4 ): "And they determined in that day, saying: Whosoever shall come up to fight against us on the Sabbath-day, we will fight against him." Therefore the precepts of the decalogue are dispensable.