Such guilt could at best be a simulation, at worst a fraud, a bogus, superficial display. Likewise the value of punishment, again unlike monetary value, depends fundamentally on the identity of the punishment's recipient. A replacement convict might offer to undergo the criminal's punishment, and might succeed in producing genuine suffering. But this suffering would have no moral value, because the fundamental point of punishment is to pay back to the criminal what she is owed. This is the element of retaliation at the heart of all punishment, even of the sort that may serve other functions, such as rehabilitation, vindication of the law or the appeasement of a watchful deity.
Retaliation is central to many Christian theories of the atonement.
Instead of repaying sinners the harm we have caused with our disobedience, a substitute is produced who offers to accept our 'sin debt,' 'bear our guilt,' and fulfil our responsibility with his own life. Even granting that Jesus was innocent, produced genuine suffering, and died, there is still the problem of the uselessness of his whole endeavour. Again, the notion of substitutive punishment is incoherent because punishment, even as defined by many Christian theories of the atonement, involves repayment, which means returning to the offender what is owed her. Hence the concept of substitutive retaliation is incoherent. To test this conclusion, imagine you are charged with the task of locating a convicted criminal so that punishment might be inflicted on her.