I recently asked Jimmy’s thoughts on a challenge to TAG. That challenge being an OT Jew that only believes in the OT books. How would a presuppositionalist respond?

Two problems:
1.) It is impossible to be neutral about the status of the New Testament. Christian Theism, as you know, presents a worldview in which the entire canon is the imperfect but providential derivation of original autographs which were divinely inspired, the whole Christian Bible standing as revelation, and therefore a worldview in which the New Testament is self-authoritative. To say only the Tanakh is revelation means one is either openly rejecting revelational epistemology, rejecting the Christian view of canon, Christian Theism by extension, or one is still living under the Old Covenant and just needs to see Jesus as its fulfillment and enter the New Covenant. If the former, it is incumbent upon the “Jew” to bring forth an alternative worldview and epistemology which can supposedly substitute the Christian one.

2.) Interlocked with problem (1), if someone wants to maintain that Jesus is not the Messiah of Genesis 3, Abraham’s heir, the Redeemer foreshadowed in the Exodus, the Deliverer of Israel archetyped by David and Esther, the Judge referenced in Ecclesiastes, and of course, the whole kit and kaboodle of the Prophets, then there is a double onus. Yes, we, the Christians, much argue as much – something pretty easy to accomplish. At the same time, the Jew must already have the means necessary to preclude the New Testament, that Jesus is the fulfillment of the Old, should he wish to reject Jesus and claim autonomy from Him. The Jew better have an answer just as much as we in OT.