fallacy
C1Formal and academic; also used in critical everyday discussion.
Definition
Meaning
A mistaken belief or idea, especially one based on unsound reasoning.
A deceptive or misleading notion; a flaw in the logical structure of an argument that renders it invalid or weak. Can also refer to a commonly held but false belief.
Linguistics
Semantic Notes
The word focuses on the falsity of reasoning or belief, not just any error. It implies a semblance of truth or logic that is ultimately invalid. Often used to critique arguments, ideologies, or popular assumptions.
Dialectal Variation
British vs American Usage
Differences
No significant lexical or grammatical differences. The concept is identical in both varieties.
Connotations
Slightly more common in UK academic/philosophical writing historically, but now equally prevalent in US equivalent registers.
Frequency
Comparable frequency in formal and academic contexts. Rare in casual conversation in both regions.
Vocabulary
Collocations
Grammar
Valency Patterns
[the] fallacy of [NP/V-ing] (e.g., the fallacy of assuming)[NP] is a fallacyto commit/commit oneself to a fallacyto fall into the fallacy of [NP/V-ing]Vocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Phrases
Idioms & Phrases
- “The fallacy lies in...”
- “To be predicated on a fallacy”
Usage
Context Usage
Business
Used to critique flawed strategic assumptions or market predictions. 'The fallacy of perpetual growth led to over-investment.'
Academic
Core term in logic, rhetoric, philosophy, and critical thinking. 'The paper identifies the ecological fallacy in the survey methodology.'
Everyday
Used in discussions to point out flawed reasoning in opinions or common beliefs. 'It's a fallacy to think that more expensive always means better quality.'
Technical
Specific named fallacies in logic (e.g., 'ad hominem fallacy', 'slippery slope fallacy', 'straw man fallacy').
Examples
By Part of Speech
adjective
British English
- The argument was fallacious from the start.
- He made a fallacious claim about the data.
American English
- Her reasoning was clearly fallacious.
- That's a fallacious comparison.
Examples
By CEFR Level
- It is a common fallacy that all snakes are dangerous.
- The politician's argument was based on the fallacy that cutting taxes always boosts the economy.
- The researcher deftly exposed the ecological fallacy inherent in extrapolating group-level data to individual behaviour.
Learning
Memory Aids
Mnemonic
Think: A 'FALL-acy' is a belief that is destined to FALL down because its reasoning is faulty.
Conceptual Metaphor
FALSE BELIEF IS A STRUCTURAL FLAW (a crack in the foundation of an argument); DECEPTIVE IDEA IS A MIRAGE (appears solid but isn't).
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Avoid translating as 'заблуждение' when it refers to a simple innocent mistake; 'fallacy' implies a logical error. 'Ошибка' is too broad. Closer to 'логическая ошибка', 'софизм', or 'ложное умозаключение'.
Common Mistakes
- Using 'fallacy' as a synonym for 'lie' (a lie is intentional deception, a fallacy can be unintentional). Confusing 'fallacy' with 'falsehood' (a falsehood is a false statement, a fallacy is flawed reasoning leading to a falsehood).
Practice
Quiz
Which of the following best describes a 'logical fallacy'?
FAQ
Frequently Asked Questions
Not exactly. A fallacy is a specific type of mistake—one in reasoning or logic that leads to an invalid conclusion. All fallacies are mistakes, but not all mistakes are fallacies.
No, the conclusion reached by fallacious reasoning might coincidentally be true, but the fallacy itself is the flawed process of reasoning. The term refers to the invalid logical structure, not the truth value of the conclusion.
Common ones include 'ad hominem' (attacking the person), 'straw man' (misrepresenting an opponent's argument), and 'false cause' (assuming correlation implies causation). 'Appeal to popularity' (bandwagon fallacy) is also very common.
The adjective is 'fallacious', as in 'a fallacious argument'.
Collections
Part of a collection
Debate Vocabulary
B2 · 48 words · Language for constructing arguments and discussions.
Critical Thinking
C1 · 49 words · Vocabulary for structured logical reasoning and analysis.
Rhetoric and Argumentation
C2 · 49 words · Advanced tools of persuasion and argumentation.