The problem with self-described “presuppositionalists” – whether they are Reformed Van Tillians or Roman Catholic papal absolutists – seems to be that they accept the Enlightenment’s criteria of epistemological skepticism and then try to reconstruct epistemological certainty from scratch. Ironically, this acceptance of the Modern way of thinking, which begins with an evisceration of metaphysics as so much “useless speculation” in need of correction by “plain facts” (i.e., for the Reformed, “biblical truth,” for the Catholic “Magisterial definitions”), is that it inevitably leads the presuppositionalist back to metaphysics. He has to ground his reconstructed epistemological certainty somewhere, so he grounds it in a brute metaphysical postulate – whether “the self-contained ontological Trinity who alone guarantees predication” (the Reformed variety) or “the self-authenticating defining authority of the Magisterium which alone guarantees knowledge of orthodox doctrine” (the Catholic variety).
Either way, because his focus is on epistemology – the conditions and limitations of knowledge – and because he gives total faith and credit to all the Enlightenment skeptical defeaters for an objectively knowable reality, he is inevitably led to contemplate the interior of his own brain in a frantic quest to find something that “makes sense” to him and upon which he can rest his deep emotional need for certainty. Whether Reformed or Roman Catholic, then, the result of the presuppositionalist method is ultimately solipsism. It’s a kind of ultimate Cartesian egocentric predicament.
It occurs to me that the way to undercut both forms of presuppositional posturing is simply to deny their initial acceptance of Enlightenment skepticism, thereby cutting off the whole fruitless self-absorptive flight into “epistemology” as the ultimate answer for all human ills. Instead, why not just assume with almost everyone prior to Descartes that we have knowledge, that our minds are “fitted” to reality and can by their very nature possess real, significant, though not comprehensive, knowledge of truth? That assumption seems to fit far better with the basic assumption of Scriptural revelation that we all make – namely, that God has spoken, and spoken in a way that we are able to understand.