Appeal to Personal Incredulity

Appeal to Personal Incredulity

Tuomas W. Manninen

I fail to understand how teachers can call themselves Christians, go to church, talk about God, talk about Christ, and then go to school five days a week and talk about Darwin, and teach it as if it’s fact, not a theory, but that’s how it happened. I don’t understand it. To me that’s talking out of both sides of your mouth.

Bill Buckingham, in Judgment Day: Intelligent Design on Trial

An appeal to personal incredulity treats an inability to understand or imagine a claim as sufficient reason to reject it (Baggini 2009; Bebbington 2011). A person’s difficulty is not itself evidence that the claim is false. Conversely, finding a claim easy to imagine does not establish that it is true. Expert explanations may help close the gap in understanding, but those explanations also need relevant evidence.

The fallacy is very commonly found in debates over science. In the Judgment Day documentary, Bill Buckingham is incredulous of how someone can both claim to be a Christian and teach science – especially Darwin’s theory of evolution (NOVA 2007). In Darwin’s Black Box, its author Dr. Michael Behe cannot see how natural selection could produce biological systems that appear to be irreducibly complex (cited in Bebbington 2011 and in NOVA 2007). But the fallacy becomes clear when we take a step back from these claims. Just because Mr. Buckingham cannot imagine how someone can be a scientist and profess Christian faith does not mean that these two viewpoints cannot be reconciled. Similarly, an inability to describe an evolutionary pathway does not by itself establish that no such pathway is possible. Assessing the biological argument requires more than a report of what the speaker finds conceivable. To be fair, Dr. Behe does qualify his statement on irreducibly complex systems by adding “… if there is such a thing” (cited in Bebbington 2011, 28).

In a variant of the fallacy, a person may appeal to her lack of understanding on a subject matter in a seemingly more self‐deprecating manner as a backhanded way of undermining expert authority. The cited political example concerns American politicians responding to questions about the scientific consensus on anthropogenic climate change. As if read from a common script, the politician has acknowledged “I am not a scientist,” only to proceed to discuss the negative impact of policies based on the scientific consensus (Chait 2014). The general pattern of the fallacy in these cases (roughly) follows these steps:

• Step 1: Politician X is asked whether or not s/he accepts the scientific consensus on topic Y.
• Step 2: X acknowledges that s/he doesn’t understand Y, because s/he is not a scientist; X defers any such question to the experts.
• Step 3: X goes on to promote her/his own initiative on Y on the grounds of economy.

Step 3 raises a separate economic question. Discussing policy costs is not itself an appeal to incredulity; the problem arises if professed lack of scientific understanding is used to dismiss the scientific claim.

When a claim seems implausible, identify what you do not understand and what evidence could resolve the question. Distinguish a gap in your understanding from a contradiction in the claim. This can be difficult when the claim challenges a valued belief, so apply the same test to your own reasoning and to an opponent’s.