October 10, 2016 by David Sutton
Shifting The Burden Of Proof, And Unfalsifiable Claims
“Shifting the burden of proof” is when one party makes an unconfirmed assertion, while putting the burden to disprove the assertion on another party. It’s a logical fallacy because it puts the burden of proof on the negative instead of the affirmative. The burden of collecting evidence to support a claim lies with the person making the claim (the affirmative), not the person challenging the claim (the negative). It is not someone else’s job to debunk an unsubstantiated claim, and the inability to refute the claim does not make it more credible.
Proving A Negative
Nobody has the burden to prove a negative in a debate, instead the onus is on the person making the positive assertion, because without evidence the negative assertion is the natural state. For example, Bob makes a positive assertion by saying, “Beyond the known universe exists a brick wall.” Leo makes a negative assertion by saying, “There is no evidence for this brick wall.” Even though it is a reasonable assumption, Leo has been careful not to assert there is no brick wall, because doing so puts him in the affirmative position. And if Bob were to suggest Leo needs to offer evidence that there is no brick wall, that would constitute shifting the burden of proof.
The Celestial Teapot
In the context of religious belief, “Russell’s teapot,” also called the “celestial teapot,” is an often cited quote by philosopher Bertrand Russell that illustrates this fallacy with an analogy.
Many orthodox people speak as though it were the business of sceptics to disprove received dogmas rather than of dogmatists to prove them. This is, of course, a mistake. 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 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.
Carl Sagan‘s “Extraordinary claims require extraordinary evidence” is also often cited to refute positive assertions without proof. If you make a claim that something exists, you must offer evidence to support it. And if that claim is bold, straying far from the norm, the evidence should equal its boldness.
Occam’s razor suggests that the fewest assumptions is the starting point for a hypothesis. An unfalsifiable claim by its nature is unable to be proved or disproved. Just because Bob can exit rational discourse and conjure this “brick wall,” or cite ancient texts of ancestors who made similar claims, does not obligate Leo to disprove Bob’s fancy. Bob’s “brick wall” hypothesis is unfalsifiable, and because of that, there could be an infinite number of possibilities to explain its existence, but without a single one offering evidence, and that means the hypothesis that makes the least assumptions is the one that posits there is no evidence for the “brick wall.”