Genetic fallacy

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Not to be confused with genetics or biological determinism.

A genetic fallacy is a logical fallacy that occurs when a claim is accepted or rejected based on the source of the evidence, rather than on the quality or applicability of the evidence. It is also a line of reasoning in which a perceived defect in the origin of a claim or thing is taken to be evidence that discredits the claim or thing itself. The fallacy is committed when an idea is either accepted or rejected because of its source, rather than its merit.


Most common:

P1: X said Y is true.
P2: X is a bad source.
C1: Y is not necessarily true.

Less common:

P1: X said Y is true.
P2: X is a bad source.
C1: Y is false.

"Second-option bias" form:

P1: X said Y is true.
P2: X is a bad source.
C1: Anti-Y is true.



The genetic fallacy is a logical fallacy but is frequently not a Bayesian one: some sources are so consistently full of it that pointing this out reasonably constitutes a refutation for all practical purposes (e.g., Scopie's law). If something is bullshit 99.9% of the time, it may not be worth investigating — especially when there are more trustworthy or pressing issues available.

Example: If Andrew Wakefield were to write a paper on anything, it can be easily dismissed.

Just Yuck[edit]

If the source's views are just so disgusting, than the genetic fallacy no longer applies.

Example: the source is a Holocaust denialist.

The source's views must be utterly reprehensible, not simply an opinion on abortion, nor Global warming denialism can reach this level of "Just Yuck".


The genetic fallacy has three subtypes:




  • "The current Chancellor of Germany was in the Hitler Youth at age 13. With that sort of background, his so called 'reform' plan must be a fascist program."
  • "I was brought up to believe in a god, my parents told me a god exists, and my parents would never lie to me, so this god must exist."
  • "Sure, the media claims that Senator Wales was reading pornography. But we all know about the media's credibility, don't we."


Can't fool me!.jpg
"The thing you said made me feel bad, so I don't think it's true and I don't think you're a nice person."

The firefighter sighed and raised the megaphone to her mouth. "Sir, you probably feel bad because you're inhaling a lot of smoke. Your house is on fire and you need to come to the window and go down the ladder with me now."

But the homeowner knew in his heart that he was a good person and a smart person and the kind of person who would never accidentally leave the stove on and drop a handtowel onto the burner. That just wasn't in character for him.[1]

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