Thomas Aquinas Commentary Galatians 3:19-20

"What then is the law? It was added because of transgressions, till the seed should come to whom the promise hath been made; [and it was] ordained through angels by the hand of a mediator. Now a mediator is not [a mediator] of one; but God is one." — Galatians 3:19-20 (ASV)

After showing by the authority of Scripture and by a human custom that the Law was unable to make a person just, the Apostle now raises and solves two questions. The second of these begins at verse 21.

Regarding the first question, he does three things:

1. He raises the question.
2. He solves it (verse 19): It was established because of transgressions.
3. He clarifies something he presupposed in his solution (verse 20).

The question that might arise from the previous discussion is this: If the Law was unable to justify, was it without purpose? The Apostle raises this question when he asks, "Why then the law?"—that is, what purpose did it serve? A Gloss notes that Augustine favors this punctuation, although he had earlier approved a different reading: "What then?" followed by, "The law was set up because of transgressions." A similar question is raised in Romans 3:1: What advantage then has the Jew? Or what is the profit of circumcision?

When he says, "It was established because of transgressions," he solves the question. Here he does four things:

1. He sets down the purpose of the Law.
2. He identifies the fruit of the Law (verse 19): until the seed should come to whom he made the promise.
3. He names the ministers of the Law (verse 19): ordained by angels.
4. He identifies the Lord of the Law (verse 19): in the hand of a mediator.

Regarding the first point, it should be noted that the Old Law was given for a fourfold purpose, corresponding to the four consequences of sin listed by Bede: wickedness, weakness, passion, and ignorance. First, the Law was given to suppress wickedness. By forbidding and punishing sin, it restrained people from sinning. The Apostle touches on this when he says the Law was "established because of transgressions"—that is, to prevent them. On this point it is said, The law is not made for the just man but for the unjust (1 Timothy 1:9).

The reason for this can be taken from Ethics IV of the Philosopher. People who are well-disposed are inclined to act well on their own, so fatherly admonitions are enough for them. Therefore, they do not need a law. Indeed, as it is said, They are a law to themselves, who show the work of the law written in their hearts (Romans 2:14).

However, people who are ill-disposed need to be kept from sin by penalties. For such people, it was necessary to establish a law that has the power to restrain.

Secondly, the Law was established to disclose human weakness. People gloried in two things: their knowledge and their power. Therefore, God left them without the instruction of the Law during the period of the law of nature. In that time, as they fell into error, their pride was confronted with its lack of knowledge, even though they still presumed on their own power.

For they said, “Many are willing and able, but there is no one to lead,” as a Gloss says on Exodus 24:8: All things that the Lord has spoken we will do. We will be obedient. Therefore, the Law was given to bring about a knowledge of sin, for by the law is the knowledge of sin (Romans 3:20). But it did not give the help of grace to avoid sin, so that humanity, bound by the Law, might test its own strength and recognize its weakness.

Finding that they were unable to avoid sin without grace, they would more ardently yearn for it. This purpose can also be derived from the Apostle's words if they are taken to mean that the Law was established to increase transgressions, in the sense that he says, Now the law entered in that sin might abound (Romans 5:20).

This is to be understood not in a causal sense but in a sequential one. After the Law entered, sin abounded and transgressions multiplied because concupiscence, not yet healed by grace, lusted after what was forbidden. As a result, sin became more grievous, since it was now a violation of a written law. But God permitted this so that people, recognizing their own imperfection, might seek the grace of a mediator. This is why the Apostle significantly says the Law was "established"—that is, interposed between the law of nature and the law of grace.

Thirdly, the Law was given to tame the sinful desires of an unrestrained people, so that, worn out by various ceremonies, they would not fall into idolatry or lewdness. Thus, Peter says, This is a yoke which neither our fathers nor we have been able to bear (Acts 15:10).

Fourthly, the Law was given as a figure of future grace to instruct the ignorant, according to Hebrews 10:1: For the law, having a shadow of the good things to come.

Next, the Apostle explains the fulfillment of the Law when he says, until the seed should come. This seed is Christ, of whom God had promised that through him all nations would be blessed. As it is written, For all the prophets and the law prophesied until John (Matthew 11:13), and, In your seed shall all the nations of the earth be blessed (Genesis 22:18).

The ministers of the Law are mentioned when he says it was ordained—that is, given in good order—by angels. This can mean the messengers of God, namely, Moses and Aaron, as it is written, They shall seek the law at his mouth: because he is the angel of the Lord of hosts (Malachi 2:7). Alternatively, "by angels" can mean through the ministry of angels, as in Acts 7:53: You have received the law by the disposition of angels.

The Law was given by angels because it was not fitting for it to be given by the Son, who is greater. As Hebrews 2:2 says, For if the word spoken by angels became steadfast... how shall we escape if we neglect so great a salvation? Which, having begun to be declared by the Lord, was confirmed to us by them that heard him.

Furthermore, he says ordained because it was given in the proper sequence: between the time of the law of nature (during which people were shown they could not help themselves) and the time of grace. Before they could receive grace, they had to be convicted by the Law.

The Lord of the Law is Christ. Therefore, the Apostle says the Law was given in the hand of a mediator, meaning in the power of Christ. This is supported by Scripture: In his right hand a fiery law (Deuteronomy 33:2), and, There is one mediator of God and men, the man Christ Jesus (1 Timothy 2:5). This mediator was represented by Moses, in whose hand the Law was given: I was the mediator and stood between the Lord and you at that time (Deuteronomy 5:5).

When the Apostle says, "Now a mediator is not of one," he explains what he meant by "in the hand of a mediator." This can be understood in three ways. First, a mediator is not of one party alone, but of two. Since Christ is the mediator between God and humanity, it was fitting that he be both God and man. If he were purely man or only God, he would not be a true mediator.

Therefore, if Christ is true God, and since no one is his own mediator, someone might suppose that there are other gods besides him, for whom he was the mediator. But the Apostle prevents this conclusion by saying that although this mediator is not of one party only, it does not mean there are other gods. Instead, God is one. Although Christ is distinct in person from God the Father, he is not distinct in nature. As it is written, Hear, O Israel: the Lord our God is one Lord (Deuteronomy 6:4), and, One Lord, one faith, one baptism (Ephesians 4:6).

A second way to understand this is that someone might believe Christ was the mediator for the Jews alone. The Apostle says that Christ is a mediator, but not of one people—that is, not only of the Jews. Rather, he is a mediator for all, capable of reconciling everyone to God, because he is God. As it says, For it is one God that justifies circumcision by faith and uncircumcision through faith (Romans 3:30), and, For God indeed was in Christ reconciling the world to himself (2 Corinthians 5:19).

A third way is that Christ is not a mediator of only one people, the Jews, but of the Gentiles as well: For he is our peace, who has made both one (Ephesians 2:14). He did this for the Gentiles by taking away idolatry, and for the Jews by delivering them from the observances of the Law. Specifically, it is not the Father or the Holy Spirit, but the Son who is the mediator; nevertheless, God is one.