Fallacy 3 of 3

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Commutation of Conditionals

F003 • Formal - Propositional Logic

Also known as: Fallacy of the Converse, Converting a Conditional

Difficulty 1/10Low LoadVery Common

Definition

Assuming that a conditional statement is equivalent to its converse.

Why Invalid

'If P then Q' and 'If Q then P' are logically independent. One can be true while the other is false.

Examples

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Scope of Applicability

  1. Identify conditional statement
  2. Check if antecedent and consequent are swapped
  3. Verify whether equivalence is claimed or assumed

Common Mistakes

  • Confusing necessary and sufficient conditions
  • Not recognizing legitimate biconditionals

Related Concepts

Affirming the ConsequentDenying the AntecedentF017

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F002 Denying the Antecedent
Return to 1.1 If-Then Reasoning