An Atonement Primer:
We may define the atonement as follows: The atonement is the work Christ did in his life and death to earn our salvation. This definition indicates that we are using the word atonement in a broader sense than it is sometimes used. Sometimes it is used to refer only to Jesus’ dying and paying for our sins on the cross. But, as will be seen below, since saving benefits also come to us from Christ’s life, we have included that in our definition as well.
The Cause of the Atonement: What was the ultimate cause that led Christ’s coming to earth and dying for our sins? To find this we must trace the question back to something in the character of God himself. And here Scripture points to two things. And here Scripture points to two things: the love and justice of God.
The love of God as a cause of the atonement is seen in the most familiar passage in the Bible: “For God so loved the world that he gave his only Son, that whoever believes in him should not perish but have eternal life” (John 3:16). But the justice of God also required that God find a way that the penalty due to us for our sins would be paid (for he could not accept us into fellowship with himself unless the penalty was paid). Paul explains that this was why God sent Christ to be a “propitiation” (Rom. 3:25 NASB) (that is, a sacrifice that bears God’s wrath so that God becomes “propitious” or favorably disposed toward us): it was to show God’s righteousness, because in his divine forbearance he had passed over former sins” (Rom. 3:25). Here Paul says that God had been forgiving sins in the Old Testament but no penalty had been paid–a fact that would make people wonder whether God was indeed just and ask how he could forgive sins without a penalty. No God who was truly just could do that, could he? Yet when God sent Christ to die and pay the penalty for our sins, “it was to prove at the present time that he himself is righteous and that he justifies him who has faith in Jesus (Rom. 3:26).
Therefore both the love and the justice of God were the ultimate cause of the atonement. It is not helpful for us to ask which is more important, however, because without the love of God, he would never have taken any steps to redeem us, yet without the justice of God, the specific requirement that Christ should earn our salvation by dying for our sins would not have been met. Both the love and the justice of God were equally important.
The Necessity of the Atonement. Was there any other way for God to save human beings than by sending his Son to die in our place?
Before answering this question, it is important to realize that it was not necessary for God to save any people at all. When we appreciate that “God did not spare the angels when they sinned, but cast them into hell and committed them to pits of nether gloom to be kept until judgement (2 Peter 2:4), then we realize that God could also have chosen with perfect justice to have left us in our sins awaiting judgment: he could have chosen to save no one, just as he did with the sinful angels. So in this sense the atonement was not absolutely necessary.
But once God, is his love, decided to save some human beings, then several passages in Scripture indicate that there was not other way for God to do this than through the death of his Son. Therefore, the atonement was not absolutely necessary, but, as a “consequence” of God’s decision to save some human beings, the atonement was absolutely necessary. This is sometimes called the “consequent absolute necessity” view of the atonement.
In the Garden of Gethsemene Jesus prays, “If it be possible, let this cup pass from me; nevertheless, not as I will, but as you will” (Matt. 26:39). We may be confident that Jesus always prayed according to the will of the Father, and that he always prayed with fullness of faith. Thus it seems that this prayer, which Matthew takes pains to record for us, shows that it was not possible for Jesus to avoid the death on the cross which was soon to come to him (the “cup” of suffering that he had said would be his). If he was going to accomplish the work that the Father sent him to do, and if people were going to be redeemed for God, then it was necessary for him to die on the cross.
He said something similar after his resurrction, when he was talking with two disciples on the road to Emmaus. They were sad that Jesus had died, but his response was, “O foolish men, and slow of heart to believe all that the prophets have spoken! Was it not necessary that the Christ should suffer these things and enter into his glory?” (Luke 24:25-26). Jesus understood that God’s plan of redemption (which he explained for the disciples from many Old Testament Scriptures, Luke 24:27) made it necessary for the Messiah to die for the sins of his people.
As we saw above, Paul in Romans 3 also shows that if God were to be righteous, and still save people, he had to send Christ to pay the penalty for sins. “It was to prove at the present time that he himself is righteous and that he justifies him who has faith in Jesus” (Rom. 3:26). The epistle to the Hebrews emphasizes that Christ had to suffer for our sins: “He had to be made like his brethren in every respect, so that he might become a merciful and faithful high priest in the service of God, to make expiation [lit. ‘propitiation’] for the sins of the people” (Hebrews 2:17). The author of Hebrews aslo argues that since “it is impossible that the blood of bulls and goats should take away sins (Hebrews 10:4), a better sacrifice is required (Hebrews 9:23). Only the blood of Christ, that is, his death, would be able really to take away sins (Hebrews 9:25-26). There was no other way for God to save us than for Christ to die in our place.
Dr. Wayne Grudem, research professor of theology and biblical studies at Phoenix Seminary, received his A.B. from Harvard University, M.Div. 
from Westminster Seminary, and a Ph.D in New Testament from the University of Cambridge. He is a board member of the Council on Biblical Manhood and Womanhood, a past president of the Evangelical Theological Society, and the author of more than a dozen books -including his magnum opus “Systematic Theology”, Grand Rapids: Zondervan, 2009 – from which this article is excerpted from chapter 27.
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