Forms of the Law
The law shows us how our lives should be lived in harmony with God and other people. Since we are sinners, it shows us how we fail to measure up to this standard. These are some forms the law takes:
1. Nature: Since nature was designed and created by God, it reflects God's glory and is a powerful witness that God exits and we are accountable to Him. Psalm 19 and Romans 1:18-32 make it clear that every person that has ever lived has experienced the law in this way. The law is evident in nature not only by looking at the sky and seeing God's power in creation. God's design for how we interact with other people is also part of nature and is still evident even in a sinful world. Even though sinful, parents still love their children, though in an imperfect way, strangers help others when their cars stall or they are in danger, etc. This is still a good indicator of how we are to behave.
2. Conscience: God gave all people a sense of right and wrong. While the conscience can be dulled by sin, it is a powerful tool to convince us of sin and righteousness. A conscience struggles to be consistent; to guide a person to treat others as he would want to be treated.
3. The gifts or grace of God. The sheer goodness of God in the gifts He gives to us convicts us of our own selfishness and greed. The supreme act of giving His Own Son for us demonstrates the law of how we ought to act and live. Romans 5:8: "But God demonstrates his own love for us in this: while we were still sinners, Christ died for us." (NIV)
4. The life of other people. When we observe the kindness of others who have helped us, it makes us examine our own lives. Great saints who have had great zeal for God, usually at great cost to their own comfort, are a powerful tool to convict us of our own selfishness.
5. The written word of God. The Bible is the final authority in all matters pertaining to God, including the interpretation of the law.
Forms of the Gospel
The gospel is the message that God loves us and through Christ's death has forgiven us of all our sins. A form of this message was first announced as a promise to Adam after the fall. Later, blood sacrifices were instituted by God as a visual reminder of the forgiveness of God. All believers before Christ trusted in the promise of a coming Savior.
While the Bible says that the law is evident to all mankind, the gospel must be spread by evangelism: the process of believers telling the lost about the forgiveness in Christ. It may seem that the gospel also should be evident to all mankind also through this reasoning: God should have immediately condemned mankind to death when it sinned against Him, but because we are still living in spite of this sin, God must be merciful. There is some truth to this, because in 2 Peter 3:15 states, "Bear in mind that the Lord's patience means salvation...". Also, the experience of Jonah at first glance might imply that the fact that God is forgiving is obvious to everyone. Jonah was resisting the call of God to go and preach the coming destruction to Nineveh because of their sin. After the whale experience, Jonah grudgingly complied, but in his bitterness he only preached law (concerning the coming destruction) to the Ninevites and left out any mention of the gospel of a forgiving God. The people guessed that God may be forgiving, repented, and God spared their city, much to the dismay of Jonah. However, the most likely explanation is that they had heard about the God of Israel and the fact that He was both a God of judgment and love; they weren't able to deduce that just from nature.
It should be clear through the Bible as well as the condition of the world today, that because of the power sin has over a person, only through the power of the Holy Spirit acting through the witness and preaching of the Word by believers will sinners be brought to conviction of sin and assurance of forgiveness. Once that occurs, it will be evident to the believer that the unexplained goodness of God is because of Christ.
The central idea of the gospel can be summarized in two points: forgiveness of sin and substitution of Christ's righteousness for ours. The Bible says that not only have our sins been removed from us, but that Christ's righteousness has become ours. We can proudly wear the robe of Christ's righteousness in the presence of God. Now, He looks at us as the beloved son in whom He is well pleased. The resurrection of Christ is proof that God has accepted this substitution. It causes great joy in our hearts.
The message of the gospel is necessary for all people including believers, not just the lost. We read it in the Bible and other Christian literature, hear it spoken and preached, sung in gospel songs and illustrated in Christian art. Christ also instituted baptism and communion so that we can experience the forgiveness of sins in a real physical and visible way.