I'm going to comment on an article by David Lewis:
I believe Lewis was often regarded as the most brilliant philosopher of his generation. In addition, he was an atheist. In this article he's both critical of penal substitution and ambivalent about it. I'd like to make a few observations:
1. I think penal substitution and vicarious atonement confront us with conflicting intuitions. It's easy to come up with illustrations in which it seems to be unjust. But it's equally easy to come up with illustrations in which it seems to be fitting. Our reaction depends on the illustration
2. It can be difficult to untangle moral intuition from social conditioning. How widespread is the intuition that penal substitution is unjust? How representative is that sentiment?
It doesn't seem to be by any means a universal moral intuition. Take revenge killings. In particular, there are cultures where, if a member of your clan murders a member of a rival clan, the rival clan will feel warranted in killing any member of your clan as just reprisal. They don't feel the need to execute the member of your clan who's actually guilty of the murder. Rather, they view the murder not so much as an attack on an individual, but an attack on their clan. So, by the same token, killing a member of your clan balances the scales of justice. Their moral perception operates at the level of the clan, not the individual. Or an individual in virtue of his relation to the clan. To attack a member of the rival clan dishonors their clan. They will avenge the murder of their clansman by killing an available representative of your clan, as the opportunity presents itself. A hapless individual who's unlucky enough to be the first representative they encounter.
Now, my point is not to condone that perspective. I'm simply pointing out that what one society deems to be intuitively wrong another society may deem to be intuitively right. Again, I don't offer that as evidence for cultural relativism in the sense of moral relativism. Rather, I used that to depict the limitations of intuitive appeals. An appeal to moral "intuition" treats intuition as a moral authority. A source of innate insight or instinctive recognition of moral truths.
And I think that's sometimes the case. The problem, though, is how to separate genuine moral intuition from cultural prejudice. When is that really intuitive, and when is that just social conditioning masquerading as the lofty notion of moral intuition?
3. Let's take another example. Suppose I murder your son. There are cultures in which you retaliate by killing my son. That actually has a tighter logic to it than the first example. It operates at two related levels:
i) Son-for-son. If you murder my son, you will suffer an equivalent loss. Executing the murderer is not equivalent.
ii) The avenger wants to make me feel the same pain I made him feel. Executing me would let me off too easy. He wants me to live so that I will experience what if feels like to lose a son. Putting me through what I put the avenger through.
It resembles poetic justice. We might say it's twisted logic, but it's not arbitrary.
Again, my point is not to endorse it, but to demonstrate the superficiality of some putative intuitive objections. We may rightly look down on these examples as reflections of a primitive honor code, but members of those cultures don't see it that way, so facile appeals to moral intuition are inadequate to adjudicate the issue.
4. Christians defend some Biblical teachings out of duty. But penal substitution and vicarious atonement are naturally compelling to many people who are not already Christian. It cuts across ethnicities and social classes. So it can't be dismissed as simply counterintuitive or morally repugnant. To say "Jesus died for my sins" has immense cross-cultural resonance. A critic might claim it's wrong, but simplistic appeals to intuition will be highly selective, inasmuch as many people don't see it that way at all.
5. Sometimes we feel pulled in opposing directions. Take a teenager who commits a really serious crime. On the one hand it's too serious to be dismissed as a youthful indiscretion. On the other hand, a part of us would like to give him a second chance. We hate to see him ruin his life so soon. What a waste!
So what's the solution? Is there a solution? He had his whole life ahead of him, but if he's made to pay for his crime–which would be just punishment–his life is shot. What if someone volunteered to take his place?
It won't do just to say that's wrong, because we're pulled in two different directions. Although it's right that he should be punished, we also wish to salvage his future.
6. Suppose I deserve to spend the next 30 years making restitution for my crime. Say that's a crime I committed as a teenager. By the time I make restitution, I will be middle-aged. I can't make up for the lost years. The lost opportunities. I can't start over again. It's too late for me.
Now, that may be just deserts, but suppose there's an alternative. Suppose a friend takes my place. But there's a catch: after making restitution in my stead for 30 years, he's rejuvenated. He reverts to the same age he was when he began.
That's different. In that case, he didn't suffer irreparable loss. So we might not feel the same way about punishing him in lieu of the actual perpetrator. The 30 years of restitution are a genuine imposition, genuine hardship, and gratuitous hardship (since he's innocent), but we haven't taken something from him that he can't get back.
Likewise, Jesus was tortured to death, but he came back to life.
7. Another consideration which Lewis overlooks is that Jesus isn't just a our peer. Rather, he's God Incarnate.
To take a comparison, suppose a general's army is captured by the enemy. The general offers himself as ransom in exchange for the POWs to secure their release. Like chess, where some pieces are more valuable than others, he's a greater prize than pawns. One general can take the place of many foot-soldiers.