 ##  [Modus Tollens](/modus-tollens) 

  ##  [Modus Tollens](https://natural.quantumdictionary.io/modus-tollens-0) 

  
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**Natural &amp; Formal Sciences Dictionary**

 
Definition

A rule of inference: from 'If P then Q' (P → Q) and 'not Q' (¬Q), infer 'not P' (¬P). It is the standard way to reject antecedents via failure of consequents.

 
 ##  [Modus Tollens](https://mathlogic.quantumdictionary.io/modus-tollens-1) 

  
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- Natural &amp; Formal Sciences -

**Mathematics &amp; Logic Dictionary**

 
Definition

A valid rule of inference that allows one to infer ¬A from premises A → B and ¬B; often stated as 'if A then B; not B; therefore not A.'