An argument can sound compelling, feel emotionally convincing, and still be completely invalid. The mechanism that makes this possible has a name: a logical fallacy. Recognising fallacies — in other people’s arguments and in your own — is one of the most immediately useful skills that critical thinking offers.
This guide covers the most common logical fallacies, with plain-language definitions and real-world examples drawn from politics, advertising, the workplace, and everyday conversation. No philosophy degree required.
If you are building your critical thinking skills from the ground up, start with An Introduction to Critical Thinking, which covers the broader framework. For practical exercises that sharpen your ability to spot fallacies in the wild, see Critical Thinking Exercises for Adults. And if you have already read the Cognitive Biases guide, you will notice that biases and fallacies are related but distinct: biases are errors in how we process information; fallacies are errors in how we structure arguments.
What Is a Logical Fallacy?
A logical fallacy is a flaw in the structure of an argument that makes its conclusion unreliable — regardless of how plausible the conclusion might seem on its surface. Fallacies come in two main varieties:
Formal fallacies are errors in the logical form of an argument. The conclusion does not follow from the premises, even if every premise is true. These are detectable by examining the argument’s structure alone.
Informal fallacies are errors in the content or context of an argument — in the relevance of the evidence, the fairness of the framing, or the accuracy of the premises. Most fallacies encountered in everyday life are informal.
The distinction matters less than the habit: whenever someone presents an argument, ask whether the conclusion actually follows from the evidence given, and whether the reasoning is being done fairly.
The Fallacies You Will Encounter Most Often
1. Ad Hominem
The pattern: Attacking the person making an argument rather than the argument itself.
The example: “You can’t take her views on economic policy seriously — she’s never run a business.” Or: “Of course he supports higher taxes; he’s just jealous of successful people.”
Why it fails: The character, motives, or background of a speaker are irrelevant to whether their argument is logically sound. A flawed person can make a valid argument. An admirable person can make a terrible one. The argument stands or falls on its own merits.
The nuance: There is a legitimate version of this concern — evaluating the credibility of a source is sometimes relevant, especially when claims are not independently verifiable. But that is a question about evidence, not a refutation of the argument.
2. The Straw Man
The pattern: Misrepresenting someone’s position — usually in a weaker or more extreme form — and then attacking that misrepresentation instead of the actual argument.
The example: “My opponent wants to reduce the defence budget.” “So my opponent wants to leave our country defenceless.” The first statement may be true; the second is a fabrication used as a target.
Why it fails: Defeating a position the other person does not actually hold proves nothing about their real argument. It is a performance of refutation, not the thing itself.
How to spot it: Ask whether the person being critiqued would recognise the version of their view being attacked. If not, the straw man is likely in play.
3. False Dichotomy (Either/Or Fallacy)
The pattern: Presenting two options as if they are the only possibilities, when in fact more options exist.
The example: “Either you support this policy fully, or you don’t care about the problem it addresses.” “You’re either with us or against us.” “If we don’t act immediately and aggressively, we’ll lose everything.”
Why it fails: Most real situations involve a spectrum of positions, partial solutions, or third alternatives that the false dichotomy deliberately obscures. The fallacy forces a binary choice where no binary genuinely exists.
Where it appears most: Political rhetoric, high-pressure sales, and any argument where the speaker benefits from eliminating the middle ground.
4. Appeal to Authority
The pattern: Using the endorsement of an authority figure as evidence that a claim is true — especially when the authority’s expertise is irrelevant to the specific claim.
The example: “Nine out of ten dentists recommend this chewing gum.” “A Nobel Prize-winning physicist says climate models are unreliable.” “My grandfather lived to ninety-five and smoked his whole life, so the health risks must be exaggerated.”
Why it fails: Authority establishes credibility in a relevant domain; it does not substitute for evidence. A Nobel physicist opining on climate science is speaking outside their expertise. A dentist endorsing a gum brand may have a financial incentive. Individual anecdote (the grandfather) is not a controlled study.
The nuance: Genuine expert consensus in a relevant field is meaningful evidence — just not conclusive proof. The question is always whether the authority’s opinion is tracking the underlying evidence or substituting for it.
5. Slippery Slope
The pattern: Claiming that a first step will inevitably lead to a chain of increasingly extreme consequences, without providing evidence for the links in that chain.
The example: “If we allow this one exception to the policy, soon everyone will be demanding exceptions, and the entire system will collapse.” “If we legalise this, it will only be a matter of time before far worse things are permitted.”
Why it fails: Cause-and-effect chains between policy decisions are empirical questions, not logical certainties. The fallacy presents a speculative cascade as if it were an inevitable one, bypassing the actual evidence about whether each step would lead to the next.
When the slope is real: Slippery slope reasoning is not always fallacious. If genuine evidence exists that one change would create pressure for subsequent changes, that is a legitimate empirical argument — not a fallacy. The test is whether the causal links are supported.
6. Circular Reasoning (Begging the Question)
The pattern: Using the conclusion of an argument as one of its premises — restating the claim rather than supporting it.
The example: “The Bible is true because it says so in the Bible.” “This investment is safe because it has never failed — and we know it has never failed because it is safe.” “He is trustworthy because he is an honest person.”
Why it fails: The argument assumes as given the very thing it is supposed to prove. No new information is introduced; the reasoning goes in a circle.
Why it is hard to spot: Circular arguments are often expressed at length, with the repetition well-disguised in different phrasing, making the loop difficult to trace.
7. Hasty Generalisation
The pattern: Drawing a broad conclusion from an insufficient or unrepresentative sample.
The example: “I met two people from that city and both were rude — they’re all like that.” “Our three biggest clients love the new feature, so users universally prefer it.” “Every economist I’ve spoken to thinks the policy is wrong.”
Why it fails: The sample is too small, too selective, or both. A valid generalisation requires a sample large enough and representative enough to support it — conditions a handful of anecdotes virtually never meet.
Why it persists: The examples cited are vivid and concrete. The statistical inadequacy is abstract. Our minds weight the concrete heavily and the abstract lightly — which is also why the availability heuristic (covered in the Cognitive Biases guide) operates so powerfully alongside this fallacy.
8. Appeal to Nature
The pattern: Claiming that something is good, safe, or correct because it is “natural,” or bad and harmful because it is “unnatural.”
The example: “This supplement is perfectly safe — it’s completely natural.” “Processed foods are bad for you by definition.” “Genetic modification is wrong because it goes against nature.”
Why it fails: Natural and beneficial are not synonyms. Arsenic, mercury, and most viruses are entirely natural. Penicillin required considerable human intervention. The origin of something tells us nothing about its value or safety without further evidence.
9. Tu Quoque (Appeal to Hypocrisy)
The pattern: Deflecting criticism of an argument or action by pointing out that the critic has done the same thing.
The example: “You’re telling me to eat healthier? You had a burger last week.” “How can the opposition criticise our economic record when theirs was no better?”
Why it fails: Whether the critic is hypocritical is irrelevant to whether their criticism is valid. Pointing at the accuser’s behaviour does nothing to address the substance of what they are saying. It is a change of subject disguised as a response.
10. The Bandwagon Fallacy (Appeal to Popularity)
The pattern: Arguing that something is true or good because many people believe or do it.
The example: “Millions of people use this supplement, so it must work.” “Everyone’s investing in this sector right now.” “The majority of people support this policy, so it must be the right one.”
Why it fails: Popularity is not evidence of truth, effectiveness, or moral correctness. History is full of widely held beliefs that turned out to be wrong — and widely popular decisions that turned out to be disastrous. Consensus is evidence when it reflects the aggregated judgement of informed experts following rigorous processes; it is not evidence when it simply reflects what is fashionable.
Fallacies in the Wild: A Quick-Reference Checklist
When you encounter any argument — in a meeting, a news article, an advertisement, a political speech — run through this mental checklist:
- Is the argument attacking the person rather than the claim? → Ad Hominem
- Is the opposing view being accurately represented? → Straw Man
- Are options being presented as if no middle ground exists? → False Dichotomy
- Is popularity or authority being used as a substitute for evidence? → Bandwagon / Appeal to Authority
- Are catastrophic downstream consequences assumed without evidence? → Slippery Slope
- Is the conclusion embedded in its own premises? → Circular Reasoning
- Is a broad claim supported only by a few examples? → Hasty Generalisation
The goal is not to become a professional debater who shuts down every conversation by naming fallacies. It is to build a quiet internal habit — a moment of hesitation when something sounds convincing but the reasoning feels thin.
The Relationship Between Fallacies and Biases
Logical fallacies and cognitive biases often work in tandem. Confirmation bias makes us more likely to accept fallacious arguments that support what we already believe, and more likely to notice fallacies in arguments we are already disposed to reject. The straw man is easier to build when in-group bias makes an opposing view seem obviously wrong from the outset. The slippery slope feels more persuasive when the availability heuristic makes the worst-case scenario easy to imagine.
This is why critical thinking is a system, not a single skill. The exercises in Critical Thinking Exercises for Adults are designed to train these components together — so that spotting a fallacy in an emotionally charged argument becomes as automatic as spotting one in a calm, abstract example.
Take the Next Step
Recognising fallacies in other people’s arguments is satisfying. Catching them in your own is the harder — and more valuable — work. That requires a structured practice environment: one where you receive feedback, work through graded examples, and build the habit under conditions that approximate the real difficulty of motivated reasoning.
My Udemy course [Your Course Title Here] covers logical fallacies and cognitive biases within a full critical thinking curriculum — including argument mapping, evidence evaluation, and applied decision frameworks.
Enrol Now on Udemy → https://www.udemy.com/course/introduction-to-logic01
(https://www.udemy.com/course/introduction-to-logic01/?referralCode=C34CEBBCC343DD1EBAAE – WITH THIS LINKED YOU GET A COMMISSION when you enrol someone else)
Think more clearly. Argue more honestly. Decide more wisely.
Related reading:
- An Introduction to Critical Thinking — The Skill That Changes How You See Everything
- Critical Thinking Exercises for Adults — 10 You Can Try Today
- Cognitive Biases: A Practical Guide for Everyday Decisions
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