Fallacy 4 of 4

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No True Scotsman

F403Informal - Evidence/Evasion

Also known as: Appeal to Purity, No True Christian, Definitional Retreat

Difficulty 3/10Low-Medium LoadVery Common

Definition

Dismissing counterexamples to a universal claim by retroactively redefining the group to exclude them, rather than accepting the counterexample as evidence against the claim.

Why Invalid

This makes the original claim unfalsifiable by definition. Instead of accepting evidence that contradicts a generalization, the arguer simply redefines the group so the counterexample no longer counts. The claim becomes circular: the group is defined by the very trait being attributed to it, making the statement trivially true but informationally empty.

Edge Cases

  • When there genuinely are established criteria for group membership that the counterexample fails to meet
  • When the original claim was clearly about a defined subset, not the general group
  • When clarifying an ambiguous term rather than retreating from a refuted claim

Examples

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  1. Look for universal claims about a group ('All X are Y', 'No X does Z')
  2. Check if counterexamples are dismissed by redefining group membership
  3. Ask whether the definition of the group changed after the counterexample was raised
  4. Determine if the modified claim is now unfalsifiable
  5. Notice if 'true', 'real', or 'genuine' is added to protect the claim
  • Confusing with legitimate definitional clarification (sometimes terms do need to be clarified)
  • Not recognizing when you yourself are using this fallacy to protect your beliefs
  • Thinking all uses of 'true' or 'real' indicate this fallacy
  • Confusing with Moving the Goal Posts (which shifts evidence criteria, not group membership)
SealioningEquivocationShifting Burden of Proof

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