Warning . . . it’s a long one:
Key to the presuppositionalist position are two psychological claims about believers and unbelievers. I’ll use “unbeliever” here as a blanket term for anyone who fails to believe that God exists, including those who believe that there is no God and those who simply don’t believe either way.
The first claim: So-called unbelievers in fact already know that God exists. Their declarations to the contrary simply manifest a kind of willful self-deception and sin.
The second claim: This knowledge manifests itself in various things the unbeliever does and says. So, for instance, when the unbeliever reasons or makes moral judgments, he betrays this implicit knowledge. He in fact constantly, without acknowledgement, “presupposes” this knowledge. Hence the name “Presuppositionalism.” [. . .]
The first psychological claim is important as it makes a big difference in how presuppositionalists approach unbelievers. Suppose you think that someone already knows that P and refuses to admit it; in that case you’re certainly more likely to treat him with disrespect or anger. Indeed, the temptation to treat him with scorn or abuse will be greater yet if you think the refusal to admit that P is due to some kind of immoral motivation. (Imagine how angry you might get at the corporate driven scientists who insists that, say, nicotine is not really addictive.)
Just to break in for a moment, I think this speaks to why atheists are so regularly strawmanned about what they do and don’t believe. You’re an atheist, ipso facto your words must always be taken with a grain of salt (i.e. relative to believers), ipso facto it is legitimate to make assertions about what you really believe, despite your protestations to the contrary. (See Witmer’s discussion of “conscious” reasoning vs. “unconscious” presuppositions, elsewhere in the article from which this extract is taken.)
On the presuppositionalist view, we already know that God exists; as a result, as they see their job, it is not so much as to offer an argument. After all, if we already know this claim to be true, we don’t need an argument. Rather, they see their job as getting us to admit what we already know. Their goal is more akin to using torture to extract a confession than it is to offer a rationally persuasive argument.
[. . .] it’s important to understand how your opponents see you; if you don’t, you can hardly hope to say something persuasive to them. It’s worth noting, too, that the presuppositionalist view of unbelievers helps explain why the actual arguments they do offer are in fact as bad as they are. They don’t really see argumentation as the main point, as they’re just trying to get you to agree to what you already know.
Witmer is an associate professor of philosophy at the University of Florida, and it’s worth reading “Atheism, Reason, and Morality: Responding to Some Popular Christian Apologetics” in its entirety as a primer for dealing with the main arguments and rhetorical ploys of some of the Christian door-to-door salesman we may run into occasionally, in the blogosphere and elsewhere. In terms of overall strategy, Witmer counsels (i) modesty (and I would add honesty) about the limits of your own knowledge on x or y subject, and (ii) “forced slowness”—never being afraid to demand that your opponents explain their questions and clarify their terms where such clarification is required. (Precisely the approach that Russell Glasser and Don Baker were critiqued for in their dialogue with a Christian apologist on The Atheist Experience.) Don’t overextend yourself, and never forget that your opponent’s main game is to trap you with your own words and make you look foolish and irrational. It’s sage advice for debate on any topic, I think.