You can't prove God doesn't exist
It is not uncommon to hear statements like, "You can't prove God doesn't exist," from apologists when they are challenged to support the claim that God exists. Such statements are an attempt to shift the burden of proof, a kind of logical fallacy.
Statements like this — which is a special case of the more general claim, "You can't prove a negative" — are based on the premise that belief in God is justified until sufficient evidence is presented to refute such existence. While this response may be considered sound under a world view which accepts the premise, this is simply a form of compartmentalization. If we were to apply that premise to all claims, we'd be unable to develop any useful picture of reality, since every claim would then have to be accepted as true (until it is disproved — a burden which is especially difficult when dealing with supernatural claims).
More tellingly, though, apologists typically only apply this premise to questions that address their particular religion — and nothing else. The same Christian, for example, who argues, "You can't prove God doesn't exist," would almost certainly reject such an attempt to shift the burden of proof if it was attempted by, say, a Hindu: "You can't prove Vishnu doesn't exist!" This compartmentalization is a form of special pleading.
A somewhat famous counter-argument was posed by Bertrand Russell when he said the following:
- "If I were to suggest that between the Earth and Mars there is a china teapot revolving about the sun in an elliptical orbit, nobody would be able to disprove my assertion provided I were careful to add that the teapot is too small to be revealed even by our most powerful telescopes. But if I were to go on to say that, since my assertion cannot be disproved, it is an intolerable presumption on the part of human reason to doubt it, I should rightly be thought to be talking nonsense. If, however, the existence of such a teapot were affirmed in ancient books, taught as the sacred truth every Sunday, and instilled into the minds of children at school, hesitation to believe in its existence would become a mark of eccentricity and entitle the doubter to the attentions of the psychiatrist in an enlightened age or of the Inquisitor in an earlier time."
Great Pumpkin Objection
Alvin Plantinga anticipates the aforementioned argument: "To put it more bluntly, no sane human being would seriously claim that because we have not disproved the existence of leprechauns or unicorns, they must therefore exist (or must be assumed to exist)."
Plantinga suggests that one could object to the validity and justification for religious belief by arguing that if belief in God can be basic, why can't any belief be basic such as belief in a Great Pumpkin? Plantinga argues that our culture and our society helps form our understandings of rationality and wants to move away from a foundationalist account for basic beliefs. There is a problem to Plantinga's response, namely the lack of a universal set of standards for judging whether a particular belief can be reasonably taken to be basic.
Shifting the argument to validating God as a basic assumption is the basis of presuppositional apologetics.