The biologist Richard Dawkins suggests that the Christian claim God became incarnate and was crucified is incongruous and improbable on its face.  The Oxford professor of philosophy, Richard Swinburne, takes the opposite view: In The Resurrection of God Incarnate he argues that there are good a priori reasons for thinking that, if there is a God, He will become incarnate in response to the obvious general fact of human sin and suffering. In other words, not only is the Incarnation and Crucifixion of Jesus not incongruous, it is precisely the sort of thing we might expect God to do if God exists. 
In my previous post I presented the first of three reasons Swinburne presents in support of his view: Given two preliminary axioms (the moral perfection of God and the sin and suffering of man) Swinburne argues that we might reasonably expect God to become incarnate and live a life filled with great suffering in order to discharge a moral obligation to share in the human suffering which, though for a good reason, He allows. In this post I will present the second reason why an incarnation follows naturally from these same axioms: To provide humanity a means of making atonement
Obligation, Guilt and Atonement
Swinburne first divides good actions into two broad types. Obligations are good actions that we owe to others: It is good in this first sense for you to feed your children and tell others the truth. Supererogatory actions are nonobligatory good actions: It is good in this second sense to volunteer at a soup kitchen. We do not wrong others when we fail to perform supererogatory actions but we do wrong others when we fail to meet our obligations—to respect each other’s property and personhood, for example, or to keep our promises. For wronging others we are blameworthy and so incur guilt. And in order to remove our guilt we need to “make atonement.”
Atonement, Swinburne says, usually has four components: repentance, apology, reparation and penance. If I have stolen your watch I must return it to you or give you something of equivalent value. Such reparation deals with the effects of my wrongdoing but it does not deal with the fact of my wrongdoing—that I sought to harm you. I must also therefore distance myself from my wrongdoing by a sincere apology and repentance.
Often this will suffice to remove my guilt but in cases of serious wrongdoing something extra may be required: a small gift or service as a token of my sorrow. Swinburne calls this “making a penance.” The process is completed when the victim agrees to treat me, insofar as he can, as one who has not wronged him: And this is to forgive me.
All Humans Have Wronged God
It is an obvious general fact, claims Swinburne, that all humans have wronged God. We have wronged God directly by failing to show reverence and gratitude to him as the holy source of our existence and we have wronged him indirectly by wronging each other. If I hit my wife I abuse the free will and responsibility entrusted to me by God and I also hurt a creature he created—just as I wrong you if I hit your child because I hurt someone upon whom you have lavished your loving care and attention.
In addition to incurring guilt through our wrongdoing we inherit a general propensity to wrongdoing. This is partly social (you are more likely to abuse your children if you yourself were abused) and partly genetic: Evidence has emerged that what a person does and has done to him at an early age affects the genes he hands on to his children.
Swinburne suggests that we also inherit something analogous to guilt: We are indebted to our ancestors for our life and for many benefits that come down to us through them; our ancestors, in turn, are indebted to God for their own wrongdoing. We therefore incur an obligation to help atone for their guilt. “Even the English law,” notes Swinburne, “requires that before you can claim what you inherit from your dead parents you must pay their debts.” Thus while the guilt itself is not ours, the obligation to atone for it is, and our failure to meet this obligation can be a further source of guilt.
It would seem, then, that human beings have a serious obligation to make atonement and are in a poor position to do so—owing to both the size of the moral debt and the propensity to continued wrongdoing. How might a morally perfect God respond to this? Swinburne suggests that God would likely respond by helping us to make a proper atonement.
The Appropriate Reparation to God
Earlier I made the obvious point that if I steal your watch I owe you a watch—or something of equal value. The question arises: What is the proper reparation for a wrongdoer to offer God? What has gone wrong, says Swinburne, is that we have failed to live good lives. One proper reparation would therefore be a perfect human life which we can offer to God in repentance. And while that one perfect human life may not morally counterbalance all the wrongdoing of n number of morally bad human lives, it is up to the injured party to determine when a sufficient reparation has been made. And one truly perfect human life would plausibly enable a merciful and morally perfect being to justifiably make that determination.
Making Sense of a Reparation Received from and Offered Back to the Wronged Party
Here the skeptic may still object that a third party cannot make restitution for the offences of another. No one would consider justice done if a judge were to have an innocent man seized off the street and thrown in jail for the crimes of the murderer who himself remained free. Correct. But the problem lies not with the argument but the analogy. Consider a more helpful one.
Suppose Mrs Hall hires a man, John, to paint her house. John is paid in advance but procrastinates providing his services and finally spends the money on a ski trip during which he breaks his leg. Ideally, he would either return the money or find someone else to paint the house on his behalf. But if he is incapable of doing either of these things (because, say, he is broke and and doesn’t know anyone prepared to paint the house) he finds himself in the position of having an insoluble debt.
Plausibly, Mrs Hall could dismiss the whole matter with an airy wave of her hand and hire a new painter. But now suppose the following: That Mrs Hall is a morally conscientious woman who thinks it important that John should take his wrongdoing seriously; that she is very generous; and that she knows someone who is prepared to paint her house on John’s behalf. No one would consider the matter resolved if she were to call this third party and engage him to paint her house without John’s knowledge: By every reasonable assessment John would still be in her debt. But she might consider the matter resolved to her satisfaction if John himself were involved in the arrangements—if, for example, he were to express remorse for the situation and then, having been provided with the contact details, were to call the third party in order to explain the problem and ask for his help.
In this analogy, needless to say, Mrs Hall represents God, John a human wrongdoer, and Jesus the third party whose assistance we must solicit. As Aquinas noted, confession and contrition must be shown by the sinner himself but, “satisfaction has to do with the exterior act and here one can make use of friends.”
Two final points.
The first is that there could by chance appear many prophets falsely claiming to be a divine offer of atonement for human wrongdoing. A prophet making the claim truthfully would therefore need the “signature” of God upon his work—an effect that only God can bring about and which can be taken as a mark of endorsement. This would show us that God, the injured party, was willing to accept the reparation. One obvious way God could do this would be to violate the laws of nature—such as by raising the prophet back to life three days after his death. 
The second final point is that the means of atonement God offers makes no difference to us unless we associate ourselves with it. Just as John, in my analogy, needs to both repent and himself solicit the assistance of the third party in order to discharge his debt, so a wrongdoer needs to ask God to accept the life of Jesus as a reparation for his sins. And this again entails the necessity of a worldwide institution to announce that God has provided a means of atonement and to enjoin us to avail ourselves of it.
Swinburne suggests that the Christian claim that Jesus saved us from our sins is to be understood in the above way. By becoming incarnate in Jesus and living a perfect life, God provided a means of atonement. Thus, “God was both the wronged person and also the one who, thinking it so important that we should take our wrongdoing seriously, made available the reparation for us to offer back to him.”
 In The God Delusion, Dawkins writes: “If God wanted to forgive our sins why not just forgive them, without having himself tortured and executed?”
 You can read my summary of the entire argument in a single post here.
 See the Resurrection of Jesus.