11 Tim 1:9–10; ²Gal 3:24; ³Rom 1:20; cf. Rom 2:15; ⁴Gal 3:10

The moral law has three main uses, viz.: (1) Theological, as it relates to all men; (2) Pedagogical, as it relates particularly to the unregenerate; and (3) Moral as it relates particularly to the regenerate. The present question deals with the second use, namely, to unregenerate men.

‘Unregenerate men’ or ‘natural men’, refer to persons who are not born again, and therefore living according to ‘the flesh’ (cf. Rom 8:8). Men are "by nature the children of wrath" (Eph 2:3) and "dead in trespasses and sins" (Eph 2:1). Christ’s elect are translated out of this state when they are born again, but the reprobate will remain in this state forever.

In this state, the conscience of man is still functioning, though it is so weak and defective that it may be said to be asleep. We say that it is functioning because firstly, the ‘work of the law’ is written in his heart (Rom 2:15); and secondly, he can still have pangs of conscience when he commits what society would regard as grosser sins, especially those for which they know might get them into trouble in this life (cf. Prov 28:1). However, we say his conscience is asleep because he would "hold [down] the truth in unrighteousness" (Rom 1:18b). In other words, because his mind is darkened and his conscience has not been quickened by the Spirit of God, he would easily suppress the truth and snuff out the voice of his conscience.

For this reason, though the natural man has sufficiently knowledge of God and His moral law to leave him without excuse (Rom 1:19-21), he will not go to God for salvation.

The first use of the law for the unregenerate is therefore to "to awaken their consciences to flee from wrath to come, and to drive them to Christ." The apostle Paul says: "Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith" (Gal 3:24).

Note that the law itself does not enable the unregenerate to please God. The apostle Paul says: "So then they that are in the flesh cannot please God" (Rom 8:8). Neither does the law in any way enable the unregenerate to earn their own salvation, for as Paul also says: "Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin" (Rom 3:20). While the Law may instruct the unregenerate on what God requires of them, they can never fulfil the law, for their heart is corrupt; and therefore all that they do are done with sinful motives and therefore sinful in God’s sight.

Note, moreover, that the law does not by itself drive the unregenerate to Christ. Many hear the preaching of the law but remain complacent and harden. However, when the knowledge of the moral law is accompanied by the powerful work of the Holy Spirit in the heart, the unregenerate is made to see how far short they fall of the glory of God and to fear the wrath of God against them. When this happens, then with the preaching of the Gospel, they are driven to Christ for salvation (cf. Acts 16:14).

From this we see that Gospel preaching must go hand in hand with the preaching of the Law. Unless the unregenerate is made to see how he has transgressed against God, he would not understand his need for salvation and the Gospel would be meaningless to him.

But what about the case of the reprobate? These may obtain a fuller knowledge of the Law through hearing or reading of it. But without the supernatural work of the Spirit in their heart, their conviction will be shallow and transient so that they do not flee to Christ for salvation. How then would the moral law be of use to them? The answer is not so much that it would make them better citizens on earth, though it sometimes happen. The answer is rather that they are left inexcusable and under the curse of the Law. The apostle Paul puts it this way: "For as many as are of the works of the law are under the curse: for it is written, Cursed is every one that continueth not in all things which are written in the book of the law to do them" (Gal 3:10).

The preaching of the Law, like the preaching of the Gospel, is like a double-edged sword. It will always accomplish its purpose. For the elect it cuts from sin, for the reprobate, it cuts from Christ. It confirms for the elect his helplessness to save himself that he may flee to Christ; it confirms for the reprobate his inexcusableness for not fleeing to Christ. W