No one understands exactly what is meant by “he made him to be sin.” How could the Son of God “be sin”? Since Paul understands Sin not as an accumulation of misdeeds, but as a Power with a death grip on the whole human race, it certainly sounds as though Jesus somehow was overtaken by the dread Power of Sin, or was assimilated to it, or was held by it in extremis — imprisoned by it in some way that was commensurate with its annihilating intentions.

