Appeal to Common Knowledge
This fallacy occurs when an arguer replaces solid evidence with the claim that a belief is widely known or universally accepted, assuming that popularity implies truth.
THE IDEA
3.6 APPEAL TO COMMON KNOWLEDGE
This fallacy occurs when solid premises are replaced with the fact that a belief is well known. It is sometimes referred to as the every child knows fallacy because it can include statements like, “even a child knows this,” or, “this is so obvious that even a child would recognize it.” Often the arguer will even appeal to “everyone” in his or her premises. However, the fact that something is widely accepted as true does not establish the truth of a conclusion. Here are some variations of this fallacy:
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The earth is millions of years old. How do I know this? Because everyone knows this!
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Every person is created equally. This is confirmed by the fact that everyone acknowledges this truth.
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Even a small child can recognize morality and immorality. So, one cannot act as if any behavior is morally ambiguous!
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Come on, everyone knows that Governor Wilkins is the best candidate for the position.
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Of course you should accept the promotion! I can hardly believe you’re asking for advice. We all know that money improves the quality of life.
A claim can be true even when this justification is inadequate. Ask what evidence supports it beyond its familiarity or popularity.
When to use it
In a political discussion, when someone says 'everyone knows that policy is bad' without providing data.
In advertising, when a commercial claims 'everyone is using this product, so it must be the best.'
In a workplace, when a manager justifies a decision by saying 'it’s obvious to everyone that this is the right move.'
In a classroom, when a student argues that a historical fact is true just because it is widely believed.
FROM THEORY TO EVERYDAY LIFE
In practice
The earth’s age
The earth is millions of years old. How do I know this? Because everyone knows this!
Moral ambiguity
Even a small child can recognize morality and immorality. So, one cannot act as if any behavior is morally ambiguous!
Political candidate
Come on, everyone knows that Governor Wilkins is the best candidate for the position.
Money and quality of life
Of course you should accept the promotion! I can hardly believe you’re asking for advice. We all know that money improves the quality of life.
A MOMENT TO REFLECT
Put it to work.
Think of a time you accepted a claim because 'everyone knows it.' What evidence could have been offered instead?
How can you distinguish between genuine common knowledge and a fallacy of appeal to common knowledge in a debate?
Why is peer pressure often rooted in this fallacy, and how can you resist it?
CONTINUE THE CONVERSATION
Source texts
- Informal Logical Fallacies A Brief Guide