I have been reading the chapter What Did the Cross Achieve? in the Collected Shorter Writings of J. I. Packer Vol. 1. I found his treatment of theological models quite helpful.
Packer raises the ‘doctrine of analogy’. This is the method of using known aspects of reality (e.g. human relationships) to explain unknown aspects (e.g. relationship to God). This doctrine operates not only in theology but in other areas too, such as the physical sciences. In the 17th century Socinus made the mistake, and so did the later reformers, of using a non-biblical analogy (16th century monarchy), to attempt to explain a divine mystery (God’s kingship), in such a way as to tie up all the logical loose ends of penal substitution. As a result penal substitution never really emerged untainted of the charge of rationalism. We have been left with the idea that God was cold and distant, and that the matter of explanation of the cross came down to the solving of a logical puzzle rather than the declaration of a gospel.
Not surprisingly, having identified this problem, Packer argues that biblical models must be adopted as foundational. These serve as the necessary controls on the dogmatic models (e.g the derived statements on the Trinity, or the dual nature of Christ) and interpretive models (e.g. penal substitution). This should lead to a more satisfying treatment of penal substitution.
In reading this I realized how easy it is to adopt non-biblical models in seeking to explain biblical truth. For example, recently I commented on The Prevailing Church by Randy Pope. The practical nature of this book left me uncomfortable with the apparent lack of biblical support. Now I think I understand why. For example, Pope uses the analogy of a business to explain the functioning of a church. It has an owner (God), an employer (elders/staff), employees (members) and customers (members/non-Christians). One would expect history to demonstrate in time that this kind of analogy will lead to real difficulties with what the people of God understand themselves to be.
Another area which springs to mind is the use of analogy in illustrating truth in a sermon. How easy it must be for the preacher to set hearers’ minds off on the wrong track while trying to keep them on it!
Packer’s work emphasises to me the need for a sound biblico-theological foundation to our thinking.