Was it appropriate for the Old Law to have been given at the time of Moses?

It seems that it was not appropriate for the Old Law to have been given at the time of Moses:

Objection 1:  As was explained above (a. 2‑3), the Old Law disposed man for the salvation that was to come through the Christ.  But man needed the remedy of this sort of salvation immediately after his sin.  Therefore, the Old Law should have been given immediately after his sin.

Objection 2:  The Old Law was given for the salvation of those from whom the Christ was going to be born.  But as Genesis 12:7 says, the promise concerning “the seed, i.e., Christ” (cf. Galatians 3:16), was first made to Abraham.  Therefore, the Law should have been given right away at the time of Abraham.

Objection 3:  Just as Christ was not born of any descendants of Noah other than Abraham, to whom the promise was made, so too He was not born of any sons of Abraham other than David, to whom the promise was renewed—this according to 2 Kings 23:1 (“The man to whom it was appointed concerning the Christ of the God of Jacob said .....”).  Therefore, the Old Law should have been given after David, just as it was in fact given after Abraham.

But contrary to this:  In Galatians 3:19 the Apostle says, “The Law was set because of transgressions, until the seed should come to whom He made the promise, being ordained by angels in the hand of a Mediator”—i.e., “being given in an orderly way,” as the Gloss puts it.  Therefore, it was fitting for the Old Law to have been handed down in that particular order in time.

I respond:  It was utterly appropriate for the Old Law to have been given at the time of Moses.  We can cite two reasons for this, given that there are two kinds of men on whom any law, whatever it might be, is imposed.  For some of those on whom a law is imposed are stubborn and proud, and these men are restrained and subdued by the law; and a law is also imposed on those who are good, and these men, instructed by the law, are aided in fulfilling what they intend.
Therefore, it was fitting for the Old Law to be given at such a time as to exhibit men’s pride clearly.  Man is proud with respect to two things, viz., knowledge and power.  He is proud with respect to knowledge in the sense of thinking that natural reason can suffice for his salvation.  So in order that man’s pride on this score might be exhibited, he was left to the guidance of his own reason without the support of a written law, and man was able to learn that he suffered from deficiencies of reason—and he learned this from experience, in virtue of the fact that by the time of Abraham men had fallen into idolatry and into the most shameful vices.  And so it was necessary for the written Law to be given after that time as a remedy for human ignorance; for as Romans 3:20 says, “The knowledge of sin comes through the Law.”
But after man had been instructed through the Law, his pride was exhibited in his lack of power (infirmitas), during the time in which he was unable to fulfill the Law which he now knew.  And so, as the Apostle concludes in Romans 8:3-4, “What the Law, weakened by the flesh, was powerless to do, this God has done by sending his own Son ..... so that the righteous decree of the law might be fulfilled in us.”
On the other hand, as far as the good men are concerned, the Law was given to assist them.  This was especially necessary for the people at a time when the Law had begun to be obscured because of the excesses of their sins.  However, assistance of this sort had to be given in a certain order, so that they might be led by the hand through what was imperfect to perfection.  And so the Old Law had to be given in the time between the law of nature and the law of grace.

Reply to objection 1:  It was not fitting for the Old Law to be given immediately after the sin of the first man, both because (a) man, confident in his own power of reason, did not yet recognize his need for the Law, and also because (b) the dictates of the law of nature had not yet been obscured by habitual sinning.

Reply to objection 2:  The Law should be given only to a people, since, as was explained above (q.  96, a. 1), a law is a communal precept (praeceptum commune).  And so certain of God’s familial and, as it were, domestic precepts were given to men at the time of Abraham.  But afterwards, when Abraham’s posterity had multiplied to such an extent as to constitute a people and had been liberated from slavery, the Law could appropriately be given.  For as the Philosopher says in Politics 3, slaves are not part of a people or political community to which it is appropriate to give a law.

Reply to objection 3:  Since it was necessary for the Law to be given to a certain people, the Law was received not only by those individuals from whom Christ was born but by the whole people marked with the seal of circumcision, which was the sign of the promise made to Abraham and believed in by him, as the Apostle puts it in Romans 4:11.  And so the Law had to be given to this people, now already gathered together, even before David.