Definition of fallacy in English:



  • 1A mistaken belief, especially one based on unsound arguments.

    ‘the notion that the camera never lies is a fallacy’
    • ‘Both writers fall into the same fallacy - basing their objections on feelings or personal experience rather than empirical evidence.’
    • ‘I can't summon the necessary faith to believe in magic if I suspect it's inconsistent nonsense, or a mess of superstitions based on fallacies.’
    • ‘This fallacy is based on the misconception that the Holy Prophet was ordered to be obeyed in his capacity of a ruler, and not in the capacity of a prophet or messenger.’
    • ‘The love it vs. leave it remark is based on a fallacy - that if you disagree with a certain policy, you must not love your country.’
    • ‘All is based upon the fallacy of global warming being caused by manmade green house gases.’
    • ‘I am sick and tired of hearing its members' boasts, which are based on a fundamental fallacy that they believe in one law for all.’
    • ‘The fashionable notion, especially on the left, that governments of all persuasions have signed up to liberal free market beliefs is a fallacy.’
    • ‘What binds all these things together is a recurring human mistake: the fallacy of total belief in the present and its technology.’
    • ‘This latest attempt to discredit Rice and Bush is based on the fallacy that because the administration was pushing hard for missile defense it must not have been taking terrorism seriously enough.’
    • ‘I didn't discover the fallacies in those beliefs, but whoever did made some Great Discoveries.’
    • ‘Much of the argument against free trade is based upon a fallacy that confuses costs and wealth.’
    • ‘But this is based on a fallacy - that the Tories support free markets across the board.’
    • ‘It is based on myths and fallacies which provide legitimacy for gross social inequalities.’
    • ‘As a pointer on the fallacies of lazy thinking based on faith rather than facts, it makes a great read.’
    • ‘Partly he draws on psychology to show the fallacy of the belief that there exists some unitary entity which can be called credibility and that dishonesty in one situation suggests dishonesty in all.’
    • ‘Wishful thinking is a fallacy that posits a belief because it or its consequence is desired to be true.’
    • ‘It helps readers to be able to easily counter the common fallacy that belief in evolution has something to do with real, practical science that works.’
    • ‘Much research has been done in the past few years into the history of Witchcraft and common beliefs proved to be fallacies.’
    • ‘As a production-oriented ideology, communism was based upon the fallacy of production itself being the ultimate purpose of economic activity.’
    • ‘Johnson's argument is based on some obvious fallacies, such as information requiring an intelligent author.’
    misconception, mistaken belief, misbelief, delusion, false notion, mistaken impression, misapprehension, misjudgement, miscalculation, misinterpretation, misconstruction, error, mistake, untruth, inconsistency, illusion, myth, fantasy, deceit, deception, sophism
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    1. 1.1Logic A failure in reasoning which renders an argument invalid.
      ‘Kraft exposes three fallacies in this approach’
      • ‘He wrote up and distributed notes on logical reasoning, fallacies, etc., and expected the students to understand what they were doing when they wrote up a proof.…’
      • ‘Dretske has denied that knowledge is closed under implication; further, he has diagnosed closure as the fallacy that drives arguments for scepticism.’
      • ‘It turns out to be a technical term in the study of logic and describes a specific type of logical fallacy, a form of circular reasoning.’
      • ‘It sounds like a classic example of the post hoc, ergo propter hoc logical fallacy.’
      • ‘Finally, yet another theory of fallacy says a fallacy is a failure to provide adequate proof for a belief, the failure being disguised to make the proof look adequate.’
      • ‘It's the old post hoc ergo propter hoc (after this, therefore because of this) logical fallacy.’
      • ‘So the knowledge argument is invalid because it involves a fallacy of equivocation: ‘know’ means something different in the two premises.’
      • ‘It's important to realise that this perspective commits a basic logical fallacy of begging the question: i.e. presenting a premise as a conclusion.’
      • ‘Beardsley thought this theory correct and used it to argue that the intentional fallacy is indeed a fallacy.’
    2. 1.2mass noun Faulty reasoning.
      ‘the potential for fallacy which lies behind the notion of self-esteem’
      • ‘This is true as far as it goes, but a vigorous application of opportunity cost reasoning reveals the fallacy of this argument.’
      • ‘The little logical fallacy that bugged me the most was the scene where the earthquake followed the Amtrak train.’
      • ‘Your argument is still emotional, and still rooted purely in logical fallacy.’
      • ‘I was under the impression that this was a forum where political issues could be discussed rationally: if you want me to be pedantic and point out every logical fallacy in every reply I've received then I'll do that.’
      • ‘This is based on a logical fallacy, which is that the population of those who would own guns if they were rare is a representative sample of the population who would own guns if they were plentiful.’
      • ‘Predictably, the appeal to personal experience is another well-known logical fallacy.’
      • ‘Entangled with the charges of fallacy and confusion made in the writings of the philosophers Davidson mentions, there are positive arguments for the compatibility of free will and determinism.’


Late 15th century (in the sense ‘deception, guile’; gradually superseding Middle English fallace): from Latin fallacia, from fallax, fallac- ‘deceiving’, from fallere ‘deceive’.