Obj. 3:  Further, the moral precepts are about the acts of all the virtues, as stated above (A. 2).  Therefore, as the Law contains, besides the decalogue, moral precepts pertaining to religion, liberality, mercy, and chastity; so there should have been added some precepts pertaining to the other virtues, for instance, fortitude, sobriety, and so forth.  And yet such is not the case.  It is therefore unbecoming to distinguish other moral precepts in the Law besides those of the decalogue.

On the contrary, It is written (Ps. 18:8):  “The law of the Lord is unspotted, converting souls.”  But man is preserved from the stain of sin, and his soul is converted to God by other moral precepts besides those of the decalogue.  Therefore it was right for the Law to include other moral precepts.

I answer that, As is evident from what has been stated (Q. 99, AA. 3, 4), the judicial and ceremonial precepts derive their force from their institution alone:  since before they were instituted, it seemed of no consequence whether things were done in this or that way.  But the moral precepts derive their efficacy from the very dictate of natural reason, even if they were never included in the Law.  Now of these there are three grades:  for some are most certain, and so evident as to need no promulgation; such as the commandments of the love of God and our neighbor, and others like these, as stated above (A. 3), which are, as it were, the ends of the commandments; wherefore no man can have an erroneous judgment about them.  Some precepts are more detailed, the reason of which even an uneducated man can easily grasp; and yet they need to be promulgated, because human judgment, in a few instances, happens to be led astray concerning them:  these are the precepts of the decalogue.  Again, there are some precepts the reason of which is not so evident to everyone, but only the wise; these are moral precepts added to the decalogue, and given to the people by God through Moses and Aaron.

But since the things that are evident are the principles whereby we know those that are not evident, these other moral precepts added to the decalogue are reducible to the precepts of the decalogue, as so many corollaries.  Thus the first commandment of the decalogue forbids the worship of strange gods:  and to this are added other precepts forbidding things relating to worship of idols:  thus it is written (Deut. 18:10, 11):  “Neither let there be found among you anyone that shall expiate his son or daughter, making them to pass through the fire:  . . . neither let there by any wizard nor charmer, nor anyone that consulteth pythonic spirits, or fortune-tellers, or that seeketh the truth from the dead.”  The second commandment forbids perjury.  To this is added the prohibition of blasphemy (Lev. 24:15, seqq) and the prohibition of false doctrine (Deut. 13).  To the third commandment are added all the ceremonial precepts.  To the fourth commandment prescribing the honor due to parents,