Sparked by an exchange about morality that arose out of a Facebook post about Kim Davis, I had a brief exchange with a self-described pre-suppositional apologist. Up until now, I'd never actually encountered one of them in real time. I've watched debates and interviews where the pre-suppositional argument is trotted out but I'd never experienced the brunt of it first hand. I know think I have a deeper understanding of what's going on.
What the hell am I talking about?
For those of you fortunate enough to have no idea what I'm talking about, the pre-suppositional argument [presup] is a method people use to convince us that their version of a god exists.
I once wrote a lengthy post explaining why the objections they were raising had merit, however they propose a solution which just about as absurd as it is possible to be, stacking nearly every logical fallacy imaginable into a very short line of reasoning. To paraphrase the great Douglas Adams, its fundamental flaws are completely concealed by its superficial flaws.
The question is not whether the argument is incorrect, but how? It fails on nearly every level, but combine that with the stubbornness of its exponents, it's hard to imagine a take-down of it that didn't require walking your interlocutor though large parts of a philosophy degree.
To give you an idea of what the argument would sound like outside of its theological domain, consider the following (hypothetical) conversation:
Me: Donald Trump won't be president.
Presup: How do you know?
Me: Because [evidence, evidence, evidence...]
Presup: But you don't know for sure?
Me: What do you mean by "sure"?
Presup: It's possible you could be wrong.
Me: I suppose it's possible. Technically, all those people voting for him wouldn't violate the known laws of physics. But it's so wildly improbable that we don't need to give that possibility any serious consideration.
Presup: So you admit you could be wrong; you don't know for sure.
Me: Well yeah, I guess.
Presup: So we have no reason to trust you because you could be wrong about that. But I know the Donald will be president. So of course Donald Trump will be president.
Strictly speaking, you have to invoke magic at some point to hold the argument to gather. Typically, the "I know Donald will be president" is justified through revelation or scripture.
Once you hear the first "How can you be sure?" all possibility for meaningful exchange is lost. The procedure loops ad infinitum like Cause and Effect because any assertion you make can be followed by "But how can you be sure?"
What's really going on?
After a while, it dawns on you that the argument isn't meant to be persuasive. It's extremely satisfying for the apologist to deliver because it seems like you're wielding a philosophical lightsaber that can cut through any argument with a simple response "But you could be wrong." What winds up happening is that your interlocutor winds up walking away in frustration and you have an ostensible victory.
Really, the argument is a form of insulation. It's a conversation stopper. Instead of an argument, it's a rhetorical device which simply prevents anyone from advancing a complex argument because at every step you get sucked back into black hole of uncertainty.
Where did it come from?
The argument arises as a response to some so valid, albeit insignificant, objections. Most reasonable people accept that it is impossible to prove negative statements. So, to bring out the popular example, I can't prove that I'm actually here writing this post and not simply a brain in a vat with electrodes stuck inside it, being made to think that I'm part of a body writing a blog post. For most of us this inability to prove our own non-brain-in-vat-ness doesn't cause us any concern and we go about our lives. But if you feel that such proof is necessary for peace of mind, your only recourse (because logic isn't going to help you) is to invoke magic. If an all knowing super powerful sky wizard could simply tell me that I'm not a brain in a vat, then I can count that as proof.
Where it all falls apart
Ultimately presuppositional apologist is a misnomer. Really it's pre-rational apologetics. They don't have a fundamental grasp of the basic terminology of epistemology. They don't understand the difference between possibility and probability, between unlikely and impossible, between plausible and proven. These mistakes in vocabulary (technically the fallacy of equivocation) allow them to claim certainty when in fact they are entitled to none. If I can't disprove that I'm a brain in a vat, they certainly can't disprove the possibility that they received a fraudulent revelation.
The one thing I kept asserting, which made my interlocutor every uncomfortable, was that evidence would change my mind. I went so far as to say that I would believe absolutely anything provided that enough evidence was presented. He was not willing to make the same admission. This is a philosophy that rejects evidence in favour of revelation. I can say confidently — and I don't think this is an ad hominem by any stretch of the imagination — if you haven't reached the point in your philosophical development where you can admit that you can change your beliefs in response to evidence, then you haven't earned a seat at the grownups' table to have philosophical discussions of this kind.
Now I post this with some sense of fear. I sent this individual a piece I had written on the subject of secular morality and was told that he forwarded it to no less than Sye Ten Bruggencate. So I live in fear that at any moment that some kind of response could turn up in my inbox.