I made the following comment on John Loftus's blog, Debunking Christianity, in reply to a commenter taking a theistic (Christian) presuppositionalist position, on a thread in which John presented a number of books that he recommends people read in 2013 for his "Debunking Christianity Challenge." It will be edited very slightly here from the original for context purposes.
By way of a short introduction, theistic presuppositionalism is the position that one is allowed to axiomatically assume, as a philosophical construct, that the bible is true in its entirety, including then that the God of the bible exists and is as depicted (probably plus whatever mess of apologetics has softened him up from being an ancient Middle Eastern battle god). The debate on the thread, which is quite long now, essentially weaves in and out of whether or not it is required to accept axioms beneath philosophical frameworks (it is), and whether or not theistic presuppositionalism is a valid axiom (it isn't). The primary reason given, not surprisingly, is that "no other philosophy," particularly empiricism (thus science) or rationalism can prove itself, although theistic presuppositionalism is complete because there are no gaps at the foundations.
At some point, I may get around to writing a post about the increasingly common theistic dodge to epistemology, which is a rather sophisticated method of shifting the burden of proof to protect a God of the Gaps. I mention that here specifically because this presuppositionalism thing, really, is one example of the phenomenon--it tries to undercut rationalism and empiricism at their epistemic roots so that theism can be shoehorned in as a bogus "default" position. Indeed, this is how this entire thread started, with the presuppositionalist asserting that no other epistemology is sufficient. For the curious, Loftus wrote another post on his blog slamming the presuppositionalist position, optimistically titled "On How to Answer a Presuppositionalist," almost as quickly as this dodge to epistemology arose.
Here's the bulk of what I wrote in the comment:
Now, here's the thing about axioms. Back in the 1930s, a fellow named
Kurt Gödel proved what is now known as his "incompleteness theorem." [Really one of two theorems.] In
very short, what that theorem says is that given any nontrivial axiomatic system, it is either incomplete or inconsistent. What
"incomplete" means is that there are true statements within the system
that cannot be proved true from within the system and that there are
false statements that the system cannot prove false. What "inconsistent"
means is that there are clear paradoxes. As a rule, we tend to pick
consistent systems and thus must be content with incomplete systems. The axioms for empiricism, for example, are consistent, as they do not
naturally lead to logical contradictions, even if they are incomplete
(in that they cannot objectively prove themselves to be valid). The
theistic presuppositionalist axiom may be epistemologically
complete--for a bad reason that I'll detail momentarily--but it is certainly not consistent. There are obvious paradoxes, e.g. the
impossibility of any omni-grade property or the combination of those.
Can this bible god make himself a sandwich so large he cannot eat it
Perhaps it is the case that people want to choose philosophical
completeness over philosophical coherence for whatever set of reasons,
but even if that's the case, it doesn't justify the theistic
presuppositionalist axiom. The problem is that these axioms serve to
create systems not that stand alone on some island but rather that allow
us to mentally interface with reality. In that, much like mathematical
axioms that could be argued to apply only to abstract concepts but yet
are still usually moored in reality, the axioms themselves can be judged
against the fruit they produce (didn't Jesus say something about that
too?) in terms of what they allow us to know. As it turns out, choosing
theistic axioms literally provides a definition for God that makes God a
problematic thing to believe in (not least because it puts God in a box, which supposedly contradicts the/another definition of God).
Euclidean geometry, for instance, could be based on all sorts of
axioms, but it is based upon five that allow for the entire construction
to follow. Those axioms were not chosen arbitrarily but rather because
it makes very good sense (and is highly useful) to have an axiomatic
system called Euclidean geometry that allows us to interface with the
abstraction of flat spaces in (read: mentally superimposed upon) our
world. If the axioms did not serve that goal, they would be rejected,
and other systems would arise instead. Ultimately, though, those systems
are themselves judged by the foundations of pragmatism--another axiom:
that which is useful has some measure of validity outstripping that
which is not. (Not, as commonly misstated, that that which is useful is
inherently good.) Indeed, there is a strong argument that we, as
creatures of limited lifespans, have an inherent bent toward pragmatism
which is itself justified by pragmatism. In a completely pure
philosophy, perhaps pragmatism isn't needed, but when you interface it
with mortal humans, it seems to be a strongly justified foundational
The law of parsimony, itself a logical axiom (that all theistic
axioms violate) is one that is often added to the milieu of logical
axioms at the foundation of understanding the world. Why? Mostly because
redundancy is wasteful, but that's not the only reason. If we're
dealing with axioms very carefully, it's simply that it's wasteful to repeat the same axiom twice. Our fundamental set of assumptions gets
bigger while providing absolutely no additional information. Indeed, if
we have two logically equivalent axioms, one can be shown to follow from
the other, and thus one of them doesn't actually satisfy the definition
of "axiom" any longer--the law of parsimony is built into the very
definition of the term "axiom," so valuable and natural is the law. Note that the law of parsimony also satisfied pragmatism in that it is inherently more useful to have minimal lists of foundational assumptions than to have overly complicated ones.
Now we can put this all together and see clearly that an axiom like
"theistic presupposition," however complete it makes someone's
philosophical framework, has a few major problems. First of all, it does
not lead to a coherent system, and this seems to be the case for all
theistic assumptions that don't point only at the God of the deist or
the philosopher (a Platonic ideal). This problem is considered generally unacceptable, and subscribing to it intentionally is literally
tantamount to saying that you don't know what you're talking about or
that you're insane. Second, when it does lead to a coherent system, in
those limited cases, it fails parsimony. This is the argument we have
had repeatedly with Randal Rauser, who insists on defining God as "a
necessary agent cause of contingent reality." The problem is that he has
to justify necessity, which he can't, and so without that real
*necessary* part, it fails parsimony. Then there's the big problem...
Theistic presupposition, indeed theistic axioms in general, utterly
fail pragmatism. They don't explain anything, and the entire point of
logical frameworks and axiomatic systems is to allow us to explain
things--they are logical constructions (i.e. mental constructions) that
allow our minds to understand reality. They're like the legend of the
map, where the map is the mental construction we have that depicts
reality. "God did it" has very weak (none, really) explanatory power and
absolutely no predictive power. To use the metaphor from earlier, it would be incorrect to say that the theistic presuppositionalist position doesn't bear fruit, but that fruit has only two uses: to feel as if an epistemic gap is closed and to feel as though a particular theistic framework is more justified than it is. To judge the tree by this fruit does not look kindly upon the tree.
This would be fine if that reflected
reality, but empiricism has already shown clearly that it doesn't. Our
world is highly predictable. Even if some god underlies the reality, the
assumption of a god lends absolutely nothing to the explanatory power
of any of our models of the world. In other words, even if there is a
god there, the assumption of a god does nothing for us. That assumption
fails parsimony. So, while this doesn't prove that there is no god
(which would be the deist's god, if any, as there is no evidence for its
interaction in the world ever at any time, whatever ancient books of
stories try to tell us), it proves that there's no valid reason to
assume that there is.
Religions like Christianity are built upon the belief, inter alia,
that one must assume the god or pay a heavy price. This, however, is a
major problem because as we see, there is no valid reason to assume the
god. This is literally a case where the god in question is screwing with
his creation--a petty tyrant that must want his creation to fail. This is
only one problem with the Christian god, though--a god which repeatedly
violates other aspects of the definition ascribed to him, like
benevolence and moral perfection, not only in the scriptures, but also
in the world at large.
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