This quote is from RC Sproul’s book The Truth of the Cross. The book is short (small hardback-roughly 6.5×4.5″) and thus far extremely helpful. I feel like I am sitting down having a coffee with Sproul.
“I have a theologian friend who frequently makes this statement: ‘In church history, there are basically only three types of theology.’ Although there have been many schools with numerous names and various subtle nuances, generically there are only three kinds of theology historically–what we call Augustinianism, Semi-Pelagianism, and Pelagianism. In basic terms, Augustinianism holds that salvation rests on God’s grace alone; Semi-Pelagianism teaches that salvation rests on human cooperation with God’s grace; and Pelagianism believes that salvation can be achieved without God’s grace. Virtually every church in history has fallen into one of those three categories.
Augustinianism and Semi-Pelagianism, in my opinion, represent significant debates within the Christian family, differences of opinion about biblical interpretation and theology among Christians. However, Pelagianism in its various forms is not an intramural issue among Christians, but is at best sub-Christian and at worst anti-Christian. I say that because of Pelagianism’s view of the necessity of the cross.
Just as there are three basic types of theology, there are three basic views of the atonement with respect to its necessity historically. First, there are those believe that an atonement is absolutely unnecessary. The Pelagians in all their forms fall into this category….These schools of thought, by taking away the reconciling action of Christ from the New Testament, are left with nothing but moralisms. For them, the cross is where Jesus died as a moral example for them. They view Him as an existential hero, as One Who brings inspiration to us by His commitment and devotion to self-sacrifice and His humanistic concerns…In Pelagianism, there is no salvation, no Savior, and no atonement because in Pelagianism no such salvation is necessary.
Second, there are those who believe an atonement is only hypothetically necessary. This view historically expresses the idea that God could have redeemed us by a host of ways and means, or He could have chosen to overlook human sin. However, He did something dramatic when He committed Himself to a certain course of action. He chose to redeem us by the cross, by an atonement. Once He committed Himself, it became necessary, not de jure or de facto, but de pacto–that is, by virtue of a pact or a covenant that God made by issuing a promise that He would do a particular thing…He was then committed to that course of action.
The third view, which is the classical, orthodox Christian view, which I am convinced is the biblical view, is that an atonement was not merely hypothetically necessary for man’s redemption, but was absolutely necessary if any person was ever going to be reconciled to God and redeemed. For this reason, orthodoxy has held for centuries that the cross is an essential of Christianity, essential in the sense that it is a sine qua non, ‘without which it could not be.’ If you take away the cross as an atoning act, you take away Christianity.
This is a helpful consignment of theological interaction. It is, as Sproul notes, timeless in its assessment and application.
You may enjoy reading the rest of the book The Truth of the Cross by Sproul. You can find it discounted here at Westminster Books.