The doctrine of imputation is not even biblical. Still less it is 'essential' to the Gospel.He goes on to (boldly) note:
I join the growing number of biblical theologians, evangelical and non-evangelical alike, who deny that Paul or any other New Testament author speaks of a righteousness of Christ (whatever it might include or exclude) that is imputed to believing sinners, and find instead a doctrine of God's righteousness as his salvific activity in a covenantal framework, not in terms of an imputation of Christ's righteousness in a bookkeeping framework.Well, I disagree with Mr. Gundry very firmly because I believe that the Scriptures do, in fact, teach that believers are imputed an external righteousness. That is, our righteousness comes outside of ourselves. Specifically, I believe the righteousness with which believers are credited is that of Jesus Christ.
So in this book, Piper goes through the NT in a very detailed exegetical fashion and proves (very solidly) that this claim by Gundry is false. It is a short book, but a very important one in understanding this assault on the historic (and biblical) view of the atonement.