Here are some quotes from J.P. Versteeg’s book Adam in the New Testament. If you would like to read my review of the book, click on the Goodreads link on the right. 

In this first quote the author is addressing the argument that Paul thought Adam was historical, but now we know he was not.  He shows that despite claims to the contrary this idea unravels Christ’s work as a historical event. 

“Therefore, if in the case of Adam the intention of Paul in his own time is divorced from its significance for us today, that must also have consequences with respect to Christ. For the redemptive-historical correlation between Adam and Christ entails that if what Paul says about Adam no longer holds for us [i.e. that Adam was a historical figure standing at the beginning of the human race], it is impossible to see why what he says about Christ in the same context must still hold for us. What is the sense of an antitype, if there is no type? What is the sense of fulfillment, if there is nothing to fulfill? The redemptive-historical correlation that Paul sees between Adam and Christ means that no longer honoring Paul’s intention when he speaks about Adam must entail no longer honoring Paul’s intention when he speaks about Christ…To no longer honor Paul’s intention when he speaks about Adam entails that the framework in which Paul places Christ and his work, collapses. 

And again, here he is quoting another author:

And suppose that Paul… did indeed believe in the historicity of the first Adam but that is this is no longer relevant for us…, because we are only interested in the function of Adam as a ‘teaching model’ why should we…not take the same view regarding the last Adam?

Versteeg brings up an interesting point regarding the guilt of man if we deny a historical Adam. Christians have held that sin entered the world because our representative head, Adam, chose to eat of the fruit in the garden. In Adam, we all sinned. There has been debate about how this works itself out, but the basic structure is essential to Christian orthodoxy. What happens when there is no historical Adam (and Eve) to sin? Here is what Versteeg says:

If Adam only lets us see what is characteristic of everyone because Adam is man in general so that the sin of Adam is also the sin of man in general, and if on the the other hand Adam may no longer be regarded as the one man through whom sin has come into the world, it is apparent that in a certain sense sin belongs to man as such. Sin thus has become a given “next to” creation…In Romans 5 Paul intends to say how how sin has invaded the good creation of God. The concept “teaching model” cannot do justice to [Romans 5]. If Adam were only a teaching model, he would only be an illustration of man in whom sin is inherent. The concept “teaching model” eliminates the “one after the other” of creation and fall, and leaves only room for the “next to each other” of creation and sin. In essence, then, one may no longer speak of the guilt of sin…Where evil thus becomes a “practically unavoidable” matter, sin loses its character of guilt. (All emphasis and punctuation is Versteeg’s).

I had not thought of the historicity of Adam from this angle before. Normally I think of Adam in reference to Christ and salvation, not man and sin. But of course, these cannot be separated. If we mess with Adam, we mess with Christ, sin, redemption, man, and as Richard Gaffin argues in his foreword, the resurrection, in the process. Where does sin and guilt come from if there was no Adam? Has it always been? Is sin inherent in man? Did God create man sinful? How can man be guilty if sin has always been? If sin has not always been, when did it enter? Who/what brought it in? 

I am convinced that a denial of a historical Adam leads naturally and logically to heresy.    As Versteeg says, 

To be occupied with the question of how Scripture speaks about Adam is thus anything but an insignificant problem of detail. As the first historical man and head of humanity, Adam is not mentioned merely in passing in the New Testament. The redemptive historical correlation between Adam and Christ determines the framework in which-particularly for Paul- the redemptive work of Christ has its place. That work of redemption can no longer be confessed according to the meaning of Scripture, if it is divorced form the framework in which it stands there.

Not all men who deny the historical Adam become heretics, but given their framework they should. Like human sexuality, the historicity of Adam is a truth worth fighting for.  To capitulate here is to begin unraveling the basics of Christian orthodoxy and most importantly to strip away the glory of Christ’s work in redeeming fallen man.