Sherem responds only to the second part of Jacob’s argument, completely abandoning his scriptural position. Why? Even in this abbreviated form, it is obvious (v. 14) that Jacob’s scriptural exegesis has been so convincing that Jacob discerns that now Sherem “know[s] [it] to be true.” Jacob has demonstrated to Sherem that the law of Moses and the other scriptures indeed teach of a Messiah.
Even though Sherem might understand that he has lost the scriptural part of the “debate,” the less well-trained among the audience might not perceive it. Therefore, Sherem presses on with his attempt to discredit Jacob but shifts his ground to the point where he believes that Jacob is most vulnerable: an appeal to divine judgment. Sherem calls what he believes to be a bluff and demands that Jacob prove his prophetic identity. Sherem asks for a proof, not because he wants one, but because he is certain that Jacob cannot provide one. Jacob’s failure will allow Sherem to deny Jacob’s prophetic calling for lack of evidence, and the hollowness of Jacob’s prophetic calling will likewise cast doubt on Jacob’s scriptural interpretations. It is a masterful move, but it is a fatal mistake.