Here is an excerpt from this book.
3 Why the Law?
In chapter 1, we saw that there are two-and only two-paths to achieving righteousness with God. One is by keeping the works of the Law-and keeping them perfectly all of the time. The other is by grace through faith. We cannot have it both ways; we must choose one or the other.
By the death of Jesus on the cross, however, Christians have been freed from the requirement to keep the Law as a means of righteousness. In addition, we are solemnly warned against going back under the Law.
We might wonder: If the Law is impossible for us to keep, and if trying and subsequently failing to keep the Law would put us under a curse, for what purpose did God give the Law in the first place? In this chapter we will study the sixpurposes for which the Law was given. Then, in the next chapter, we will consider the effects that the Law produces in the lives of those who try to keep it.
1. Not As a Means to Righteousness
It is important for us to begin with the reason for which the Law was not given. God never expected anybody to achieve righteousness by keeping the Law. Paul states this clearly: "Therefore by the deeds of the law [the keeping of the Law] no flesh will be justified in His sight" (Romans 3:20). Other than Jesus, who kept the Law perfectly, no other human being will ever achieve righteousness by keeping the Law.
Two passages in Galatians make this clear: "A man is not justified by the works of the law" (2:16), and "that no one is justified by the law in the sight of God is evident" (3:11). The Bible is clear: No one, apart from Jesus, ever will be justified or achieve righteousness in the sight of God by keeping the Law. If the Law was not given to make us righteous, then why was it given?
2. To Reveal Sin
The Law was given as God’s diagnostic means to reveal sin. When you go to a doctor today and tell him, "Doctor, I feel kind of strange inside and I get dizzy spells," he does not reach up to the shelf, pull down a little bottle of pills and say, "Here, take these."
Before he gives you medicine he says, "First of all, we’ll find out what’s wrong with you." Today, going to doctors usually involves an agonizing series of tests. They draw blood, take a urine sample, use different imaging techniques, put the whole picture together in order, they hope, to arrive at a diagnosis of what is wrong with you. A good doctor diagnoses your ailment, and then prescribes the treatment. It is futile to offer medicine to somebody until the problem has been diagnosed.
The Law is God’s diagnostic instrument. He uses it to show us what is wrong with us. We return to Romans 3:20: "Therefore by the deeds of the law no flesh will be justified in His sight, for by the law is the knowledge of sin." What does the Law do? It makes us aware of sin. Paul adds, "What shall we say then? Is the law sin? Certainly not! On the contrary, I would not have known sin except through the law" (Romans 7:7). The only thing that revealed sin to Paul was the Law.
Has then what is good become death to me? Certainly not! But sin, that it might appear sin, was producing death in me through what is good, so that sin through the commandment might become exceedingly sinful. verse 13
The purpose of the Commandments and ordinances was to bring sin out into the open and to reveal sin in its true nature as deceptive, destructive and deadly. Until we really see the nature of sin we are not going to see fully our need of salvation. You must know you are sick before you will be willing to take the doctor’s remedy. Jesus said, "I didn’t come to call the healthy, but the sick. I didn’t come to call the righteous, but sinners" (see Matthew 9:12-13). The Law shows us the nature, operation and effects of sin, "so that sin through the commandment might become exceedingly sinful" (Romans 7:13). God gave the Law so that we would see this evil force of sin in all its horrible working and with all its deadly effects.
This is of particular interest to me because when I was a professional philosopher, my primary studies were in the philosophy of Plato, which I studied in great detail for many years. Plato was about the most intelligent man, by way of pure intellect, that I encountered in my studies. Basically, his philosophical theory was that knowledge is virtue. If only we know what is right, that is all we need. Well, that is obviously wrong, because lots of people know clearly what is right and still do what is wrong.
Is it not amazing that so great an intellect as Plato could not see that simple fact? Why did he not see it? Because he had nothing to reveal the nature of sin to him. He did not have the diagnostic, which is the Law of God. We should praise God every day for the revealed Word of God in the Bible, because it is the only book that offers us the correct diagnosis of our problem. Plato could not see the true nature of the human condition because he did not have the truth of the Bible available to him. The Law is given to bring sin out into the open and to show it in its true nature and character.