[American Constitutionalist]

" What's so interesting to me is this desire for an alternate mediator has existed from the beginning of Christianity. "

That's because GOD's way through Christ is so strict, so narrow, and that mankind has a inability to accept the fact that all of us are guilty in front of a HOLY GOD and are not willing to come to a end of themselves and ask for GOD's mercy and grace alone in Jesus Christ.
That's why many people won't or will not accept Christ, because they do not want to humble themselves and admit to GOD that they are wrong, that they are guilty are worthy of eternal punishment and damnation in hell.
They are not willing to believe that GOD provided a way out, and that is Jesus Christ.
Another element in that is that man kind has a bad habit to think that some how man still has to put his own 2 cents worth in their effort to their salvation.. some how they feel they have a need of their own effort to be accepted by GOD, and in this article, Cain's efforts was not accepted by GOD, ABLE's was.
Cain's sacrificed was made by his own hands, ABLE's was made by GOD himself.

[caww]

mankind has a inability to accept the fact that all of us are guilty in front of a HOLY GOD and are not willing to come to a end of themselves and ask for GOD's mercy and grace alone in Jesus Christ.

Although this is quite true..it is here that the conviction of the Holy Spirit comes in. It is indeed Gods work when He convicts us. And we must remember each has their appointed time. God knows when this is and if or not they will be receptive. Often it does take more than one encounter of truth to the heart and mind. Even His disciples did not get the truth right away.