In the Prima Secunda of his Summa Theologica, Q. 98, articles 1 and 2, Thomas Aquinas answers these questions. In the first article, Aquinas affirms that the Law was indeed good even though Ezekiel says that God “gave them statutes that were not good, and judgments in which they shall not live” (20:25). It seems as though Revelation is against Thomas here, but he makes a distinction. Namely, the Laws “that were not good” refers to the ceremonial precepts. They were not good because they did not confer the Grace necessary for the remission of sins. Another “not good” aspect of this Law is that, as Aquinas mentions, it caused concupiscence to increase “since we desire a thing the more from its being forbidden.” And when a desire wants what is forbidden, this disordered desire leads to sin. So how then is the Law good? Here Aquinas makes a distinction between degrees of good:
-A perfect good: a good which is sufficient in itself to bring about the desired
-An imperfect good: a good that is of some assistance in attaining the
end, but not sufficient in itself for its acquirement.
The end of the Divine Law (of which the Old Law is part) is “to bring man to that end which is everlasting happiness.”
Hence, the Old Law is an imperfect good that points to the end of everlasting happiness, and provides assistance, but is in itself insufficient to reach such end.
If you are keeping score, we now have an Old Law which not only is imperfect, but leads to sin. How can such a Law possibly be from God?
First, Aquinas tells us that the Old Law was ordained to Christ in two ways:
1) It bears witness to Christ.
2) It withdrew men from idolatrous
worship and taught them to worship the One God.
Thus, the Old Law has to be from God. “For the devil would not make a law whereby men would be led to Christ, Who was to cast him out….Therefore the Old Law was given by the same God, from Whom came salvation to man, through the grace of Christ.”
Building upon the previous conclusion, Thomas affirms the words of St. Paul in the Letter to the Galatians (3:24), “The law was our pedagogue in Christ.” The Old Law prepared us for the Grace of Christ. It was a Law that was humanly impossible to keep, but Christ would come and write a New Law on our hearts and give us the Grace to make it possible to keep the Divine Law. Apart from the Grace of Christ, we are unable to obtain Salvation. This is the heresy of Pelagius, who thought that some men did not need Christ’s Grace, but were able to reach Salvation on their own. God gave the Old Law precisely so men would not fall into this Pelagian way of thinking.
God wished “to give such a law as men by their own forces could not fulfill, so
that, while presuming on their own powers, they might find themselves to be
sinners, and being humbled might have recourse to the help of grace.”
The Divine Pedagogue that was the Old Law was designed to show men how weak and sinful they really were in order for them to recognize that they needed God and the Grace that only comes from Christ. In Romans 1, Paul tells us that the pagans did not pick up on the necessity of humbling themselves, but rather gave in to the sin of pride and “although they knew God they did not honor him as God or give thanks to him, but they became futile in their thinking and their senseless minds were darkened. Claiming to be wise, they became fools, and exchanged the glory of the immortal God for images resembling mortal man or birds or animals or reptiles…they exchanged the truth about God for a lie and worshiped and served the creature rather than the Creator..” (Rom 1: 21-23, 25).
In article 2, Aquinas also seems to suggest that the fathers of old had some kind of faith in Christ. For he says:
“Although the Old Law did not suffice to save man, yet another help from God
besides the Law was available for man, viz. faith in the Mediator, by which the
fathers of old were justified even as we are.”
This is an odd suggestion that is found elsewhere in the Summa where Aquinas suggests that Adam and Eve had a pre-lapsarian awareness of the Grace of Christ.
The ways of God are truly wonderful! By showing us our weakness we come to recognize our sinfulness and our absolute need of His love and Grace given by Our Lord Jesus Christ.