Definition of modus tollens in English:

modus tollens


  • 1The rule of logic which states that if a conditional statement (‘if p then q’) is accepted, and the consequent does not hold (not-q) then the negation of the antecedent (not-p) can be inferred.

    • ‘Only universal claims are susceptible to the application of modus tollens that underlies falsifiability.’
    • ‘Some philosophers have defended the view that animals are not sentient and attempted to use a component conditional for modus tollens.’
    • ‘From a conditional statement, one can construct two types of valid inference: modus ponens and modus tollens.’
    • ‘First, although modus ponens has a probabilistic analog, modus tollens does not - the fact that a hypothesis says that an observation is very improbable does not entail that the hypothesis is improbable.’
    1. 1.1 An argument using the rule of modus tollens.
      • ‘This argument has the modus tollens form, and hence is valid - if its premisses are true, then its conclusion must be true as well.’
      • ‘Once this is shown, the consequences invite a modus tollens; the mere vulnerability of proposed reductions is hardly enough to support the view with such exotic consequences.’
      • ‘But when dealing with probabilistic arguments, such as found in the intelligent design approach, modus tollens does not hold anymore.’
      • ‘One use of modus tollens is the reductio ad absurdum argument, i.e. showing that a premise is false by demonstrating that it implies an absurd conclusion.’
      • ‘So, by modus tollens, I don't know that I have hands.’


Latin, literally ‘mood that denies’.


modus tollens

/ˌməʊdəs ˈtɒlɛnz/