The Perfection of the Moral Law

(Excerpts of Francis Turretin, in modern English)

Francis Turretin taught that the moral law of God, summarized in the Ten Commandments, is perfect, complete, and unchangeable. By “perfect,” he did not mean that sinners can keep it perfectly, but that the law itself lacks nothing. It fully expresses what God requires of human beings in every age.

1. The Moral Law Is Complete and Lacks Nothing

The moral law contains everything necessary to direct us in loving God and loving our neighbor. Nothing needs to be added to it, and nothing may be taken away from it.

“The law of the LORD is perfect, reviving the soul” (Psalm 19:7)

God did not give a partial rule for life. His law reaches every duty, whether toward God (the first table) or toward other people (the second table). All righteous behavior can be traced back to its commands.

2. The Moral Law Is Spiritual, Not Merely External

Turretin emphasized that the law governs not only outward actions but also the heart, thoughts, and motives. God is not satisfied with external obedience alone.

“The law is spiritual, but I am of the flesh” (Romans 7:14)
“You shall not covet” (Exodus 20:17)

Even sinful desires, inward corruption, and secret thoughts fall under the law’s authority. This shows the law’s depth and perfection—it reaches where human laws cannot.

3. The Moral Law Is Universal

The moral law applies to all people, in all places, at all times. It was written on Adam’s heart at creation and remains binding today.

“They show that the work of the law is written on their hearts” (Romans 2:15)

Ceremonial laws were temporary, and civil laws were specific to Israel as a nation, but the moral law flows from God’s unchanging nature, and therefore it cannot change.

4. The Moral Law Cannot Be Abolished

Turretin strongly rejected the idea that the moral law was abolished by Christ. Christ fulfilled the law, but He did not destroy it.

“Do not think that I have come to abolish the Law or the Prophets” (Matthew 5:17)

Christ removed the law as a means of justification, but not as a rule of life. Believers are no longer under the law for condemnation, but they are still under it for obedience.

5. The Law Reveals Sin and Drives Us to Christ

The perfection of the law exposes our imperfection. Because the law is holy and strict, it shows us our guilt and our need for a Savior.

“Through the law comes knowledge of sin” (Romans 3:20)
“The law was our guardian until Christ came” (Galatians 3:24)

The law does not save, but it prepares us for salvation by humbling us and pointing us to Christ.

6. The Moral Law Is a Rule of Gratitude for Believers

For the believer, the law is no longer a burden of fear but a guide for thankful obedience.

“If you love me, you will keep my commandments” (John 14:15)

The Holy Spirit writes the law on the heart, enabling believers to delight in God’s will—not perfectly in this life, but sincerely.

“I delight in the law of God, in my inner being” (Romans 7:22)

7. The Law Reflects God’s Holy Character

Ultimately, the moral law is perfect because it reflects who God is. God is holy, righteous, and good, and His law mirrors His nature.

“So the law is holy, and the commandment is holy and righteous and good” (Romans 7:12)

To attack the law is to attack God’s holiness itself.

Summary in One Sentence

The moral law is perfect because it fully, spiritually, universally, and eternally reveals God’s righteous will—condemning sinners, driving them to Christ, and guiding believers in grateful obedience.