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The Fullness of God's Law

WSC Q.41. Wherein is the moral law summarily comprehended? A. The moral law is summarily comprehended in the Ten Commandments.

Question 41 of the Westminster Shorter Catechism explains that the Ten Commandments summarize the moral law.

What is the moral law? The moral law is a reflection of God’s character. The moral law shows us what is good, right, and true according to the character of God.

God reveals the moral law in two ways: implicitly in creation and explicitly in his Word.

This law was first written on the heart of man at creation. In Romans 2:14-15, Paul explains that even those who do not have the written law of God still have the law of God written on the heart. God has implicitly (clearly but not through words) revealed this law in the heart. Humanity innately has an understanding of what is good, right, and true. Post-fall, our sin loves to misinterpret and reinterpret this law; nevertheless, it is still revealed in man. Man has an innate understanding of good, but he also has a sinful propensity to rebel against that understanding.

Whereas the moral law written on the heart is implicitly revealed, God’s spoken revelation of the moral law explicitly tells sinful man what is good, right, and true. This explicit revelation of the moral law is summarized in the Ten Commandments, which summarize what is good, right, and true. By extension, the Ten Commandments reveal what God is like.

The Ten Commandments (and the moral law) can be summarized further. Jesus explains in Matthew 22:34-40 that the whole law hangs on the commandments to love God and neighbor. This other-centered, God-centered love is a revelation of who God is. God, for all eternity, has had an other-centered, God-centered love within the Trinity.

With these things in mind, we might say that God’s character is revealed in the moral law, which is summarized in the Ten Commandments, which is summarized in a love of God and neighbor.

Summary in Nature

To understand the fullness of the moral law, we need to understand that the Ten Commandments are only a summary of the moral law.

One test case helps demonstrate the summary nature of the Ten Commandments.

In Romans 13:1, Paul writes, “Let every person be subject to governing authorities.” In verse 7 he continues, “Pay to all what is owed to them: taxes to whom taxes are owed, revenue to whom revenue is owed, respect to whom respect is owed, honor to whom honor is owed.” Paul commands the Romans to respect, honor, and be subject to positions of authority. But where is this found in the Ten Commandments? If the Ten Commandments provide an exhaustive list of the moral law, we should expect to find a command concerning government. Yet, there is none.

However, suppose the Ten Commandments are a summary of the moral law. In that case, we can see that the command to honor the most fundamental authority in society, parents, represents the honor we should give to all positions of authority, like government.

With this in mind, how are we to understand the fullness of the moral law summarized in the Ten Commandments? To understand the fullness of the moral law, we must understand that the Ten Commandments have inward, inverse, and broad applications.


First, the Ten Commandments have inward application. In the Sermon on the Mount, Jesus explains that true morality is not just outward but inward. Mere outward observance of the Ten Commandments is not a reflection of true morality. In Matthew 5:21-22 we read, “You have heard it was said to those of old, ‘You shall not murder; and whoever murders will be liable to judgment.’ But I say to you that everyone who is angry with his brother will be liable to judgment….” Inward hatred of neighbor is akin to outward murder of neighbor. He goes on in verses 27-28, “You have heard it was said, ‘You shall not commit adultery.’ But I say to you that everyone who looks at a woman with lustful intent has already committed adultery with her in his heart.” Inward lust of a woman is akin to outward adultery with a woman. Mere external observance of the Ten Commandments is not obedience; to reflect God’s character, a person must be inwardly obedient from the heart.


Secondly, the Ten Commandments have inverse applications. The first commandment states, “You shall have no other gods before me” (Deut 5:7). This is a negative statement. “Don’t worship other gods,” God commands. However, the inverse is undoubtedly true as well. “You shall worship God alone.” Whenever a command is spoken in the negative, the positive is also true. Likewise, whenever a command is spoken in the positive, the negative is also true.

For another example, the eighth commandment states, “And you shall not steal” (Deut 5:19). The inverse of this would be that you should protect and promote your neighbor’s possessions. Paul demonstrates this truth in Ephesians 4:28. Paul writes, “Let the thief no longer steal, but rather let him labor, doing honest work with his own hands, so that he may have something to share with anyone in need.” Not only should the thief stop stealing, but the thief should also start working to provide for others in need. The inverse of the commandments also reflect moral goodness.


As we saw in the earlier example with the command to honor authority, the commandments also have a broad application. We noticed that the commandment to honor parents is representative of the broader command to honor positions of authority. We can see this principle in the other commandments as well. The third commandment requires that “You shall not take the name of the LORD your God in vain…” (Deut 5:11). We are commanded not to take God’s name lightly; the inverse application of this is that we should reverence God’s name. But is it only God’s name we should reverence? The whole of Scripture demonstrates that this command has a much broader application. We should have a reverence for all the things of God. We should not take his Word, his worship, his provision of a Savior, his ordinances or any of the things of God lightly. God does not make light of these things, and neither should we.

The Weight of the Law

Understanding that the Ten Commandments have inward, inverse, and broad applications further demonstrates our great guilt before God. Many people could say they have never stolen something, but have they protected the private property of their neighbor they way they should? Many people could say they have never committed adultery, but have they ever lusted after a woman? The inward, inverse, and broad applications of the Ten Commandments should cause us to cry out with Isaiah, “Woe is me! I am undone.” The full weight of the law is an unescapable burden to the sinful soul. This burden then drives us to the only savior, Jesus Christ. Only Jesus can bear the brunt of the full condemnation of the law for us in our place. Only Jesus perfectly obeys the Ten Commandments in our place. Our great guilt shows us the great price he paid to redeem sinful souls. We must have Christ as savior, and we have him through faith alone!

Additionally, the saved sinner should want to understand the fullness of the Ten Commandments. The law cannot save us, only Christ does that, and he does it fully and perfectly. Part of the salvation secured by Christ is the work of God conforming us back into the image of God. The Ten Commandments reflect what our God and Savior looks like. The Ten Commandments show us what goodness is. The Christian is being sanctified to greater obedience to the Ten Commandments. The Christian is increasingly conformed to the consummate image of God, Jesus Christ. The Christian has hope that one day, in glory, he will fully obey the Ten Commandments. The Christian has hope that one day, in glory, he will be able to fully reflect God’s goodness as the image of God.

Applying the Ten Commandments inwardly, inversely, and broadly helps us to understand the fullness of the Ten Commandments. The fullness of the Ten Commandments in turn demonstrates to us our need for a savior, the greatness of our savior, and what it looks like to be conformed into the image of our savior.

Below is a resource where I attempt to display the inverse and broad applications of the Ten Commandments. I hope it will be helpful to show us our great sin and our great savior, Jesus Christ.


Stephen Duarte (ME, National University; working on MTS, Reformed Baptist Seminary) is a pastor at Parkside Bible Fellowship in Fallon, NV. He is husband to Debbie and father of three.


Note: The views expressed in this article are that of the author and do not necessarily reflect the views of other contributors on this site.


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