"Penal substitutionary atonement" refers to the doctrine that Christ died on the cross as a substitute for sinners. God imputed the guilt of our sins to Christ, and he, in our place, bore the punishment that we deserve. This was a full payment for sins, which satisfied both the wrath and the righteousness of God, so that He could forgive sinners without compromising His own holy standard. (Explained in this article on theopedia.com.)

There are many objections to the doctrine, as noted in the article, not the least among them being that the concept is unjust. Yet proponents have adequate scripture to show that this is how the Christian god was able to forgive sins.

I heard a story that illustrates the concept some time ago, and was able to find it on the  Internet. It goes like this:

Quote

In the mountains of Virginia years ago there was a boy's school class which no teacher could handle. The boys were so rough that the teachers resigned. A young teacher applied for the job. The old school director scanned him up and down, then said, "Young fellow, do you know what you are asking for? An awful beating, that's what. Every teacher we've had up there gives up in defeat. The young teacher replied, "I'll risk it. Let me try."

Well, when he appeared for duty in the little school, one big fellow, Tom whispered out loud, "I won't need any help; I can lick him myself."

The teacher said, "Good morning. We have come to conduct school." The students yelled a sarcastic "Good Morning" back at the teacher at the top of their lungs.

"Now, I want a good school," the teacher continued, "but I confess, I don't know how unless you help me.” Suppose we have a few rules. You tell me and I'll write them on the blackboard."

One fellow yelled, "No stealing!" Another chipped in, "On time!" Finally ten rules appeared. "Now, said the teacher, "a law is not good unless there is a penalty attached. What shall we do with the one who breaks them?" "Beat them across the back ten times without his coat on!" came the shout.

 

"That is a pretty severe punishment boys, are you ready to stand by it?" A yell in the affirmative greeted the teacher. "All right", said the teacher, "then school comes to order."

In a day or so "Big Tom" found his dinner was stolen. Upon inquiry the thief was located - a little hungry fellow about ten. The next morning the teacher announced, "We have found the thief and he must be punished according to your rule - ten stripes across the back! Jim, come up here!"

The trembling little fellow came up slowly with a big coat, buttoned and pinned up around his neck. He pleaded, "Teacher, you can lick me as hard as you like but please don't make me take off my coat."

"You helped make the rule," reasoned the teacher, “take the coat off."

"Oh teacher, don't make me!" he begged, but the teacher's stern face showed no leniency, so he began to unbutton. And what did the teacher behold? The lad had no shirt on and only strings for suspenders over his bony little body.

"How can I whip this boy?" thought the teacher. "But I must do something if I am going to keep this classes respect."

Everyone was quiet. "How come you came to school without a shirt, Jim?" asked the teacher.

"My father died, and we ain't got much. I only have one shirt, and mother's washing it today, so I wore my brother's coat to keep warm."

With a sigh of a heavy heart, the teacher hesitatingly grasped the rod in his hand. Just then "Big Tom" jumped to his feet and said, "Teacher, if you don't mind, I'll take Jim's licking for him."

“Very well, there is a certain law that one can take another's punishment for him. Are you all agreement?"

With the classes consent Tom removed his coat, and after five strokes the rod broke. The teacher bowed his head and thought, "How can I finish this awful task?"

Then he heard the entire class sobbing and what did he see? Little Jim had reached up and caught Tom with both arms around the neck. "Tom, I'm awful sorry, Tom, I was so hungry. I'll love you till I die for taking my licking for me. I'll love you forever!"

Yes there is a certain law that one can take another's punishment for him. The wages of sin is death, but the gift of God is eternal life, through Jesus Christ our Lord.

Author Unknown

The story, even though it's just a story, is repulsive. It's easy to point out why: First, the prescribed punishment is the same regardless of the crime. Second, even if all of the "crimes" were the same, the prescribed punishment is way out of proportion to any of the infractions that it's supposed to apply to. And, finally, although Big Tom is the certainly to be commended for his actions, no justice is done by punishing him. Hence the argument from many theologians that penal substitutionary atonement can't be how Jesus' sacrifice works, because it wouldn't result in justice.

But that argument is based on today's sensibilities. Of course you can't punish one person for another's crime! It's not like there's some cosmic imbalance that simply needs to be satisfied -- a crime was committed and the universe won't be right until some punishment has been exacted. We know better than that.

The problem is that those who turn to scripture to teach this doctrine are correct. That's actually what the Bible teaches. The linked article mentions these passages (among others):

• 2 Corinthians 5:21 - "For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God."
• Galatians 3:13 - "Christ redeemed us from the curse of the law by becoming a curse for us -- for it is written, Cursed is everyone who is hanged on a tree."

And while objectors come up with other hypotheses about how Jesus' death saved people from sins, they have to jump through a lot more hoops to make their points using the Bible, and they have to claim that certain Bible passages don't really mean what they say.

But well they should object! As in the illustration about the Virginia school, it isn't only that penal substitutionary atonement is unjust, it's that the "wages of sin" in the Bible far, far exceed any crime that could ever have been committed. In the Bible, one lie told by a 12 year old merits infinite torment -- a literal never ending Hell. It's easy to see that this punishment is unjust, yet when I was a Christian these concepts were just assumed to be obvious. I never heard anyone question them, because just like from childhood we were told that it's obvious the Christian god is real, we were also told that everyone actually deserves to go to Hell.

But rather than argue, as some theologians dp, that these concepts can't really be what the Bible is getting at, this is another case where we should just accept the obvious: This is mythology. Some ancient people actually believed these things, they got written down, and due to changing political climates and 2000 years of evolution of the religion which has allowed it to hang on despite humanity's advancement, people still believe them. Because they describe these things as being "just," and we understand today that they are horribly unjust concepts, it should be obvious to us that they aren't true -- that the Bible is obviously not the word of any sort of god.