What a fallacy is
A logical fallacy is an error in reasoning: a pattern of argument that looks convincing but does not actually support its conclusion. Fallacies are common in advertising, politics, workplace debates and family arguments, often without anyone intending to mislead.
Two cautions come first. A fallacy shows that an argument is weak, not that its conclusion is false; someone can reach a true conclusion by a bad route. And fallacy names are tools for your own thinking, not weapons. Pointing at a flaw is only useful if you also engage with the actual point.
Attacking the person (ad hominem)
This replaces a response to the argument with an attack on the person making it.
Example: “You can’t trust her budget proposal; she once got a number wrong in a meeting.”
Whether a proposal is sound depends on its content. A person’s flaws, record or motives can be relevant when the claim depends on their honesty or expertise, but they do not settle whether the argument works.
The straw man
A straw man misrepresents someone’s position in a weaker form and then attacks that version.
Example: A says, “We should spend a bit less on the office party.” B replies, “So you want to cancel all fun at work?”
To avoid it yourself, restate the other person’s view in terms they would accept before you respond. This is also an ingredient of respectful disagreement.
The false dilemma
This presents only two options when more exist.
Example: “You’re either with us or against us.”
Real situations usually have middle paths, partial answers and third options. When you see a pair of choices offered, ask what else is possible.
The slippery slope
This argues that one step will inevitably lead to a chain of increasingly bad results, without showing that each link is likely.
Example: “If we let students retake one quiz, soon nobody will take any test seriously.”
Some chains of consequences are real, so the important question is whether each step is actually probable. Without that, the argument is mostly fear.
Appeal to popularity
This claims something is true or good because many people believe or do it.
Example: “Millions of people use this product, so it must be the best.”
Popularity can be a clue, since many people may have good reasons, but it is not proof. Crowds have been wrong often, and they may all be influenced by the same marketing or the same assumption.
Appeal to authority
Relying on an expert is often reasonable, but it becomes a fallacy when the person is not an authority on the topic, when experts truly disagree, or when the claim is that something is true only because someone important said so.
Example: “A famous actor says this supplement works, so it does.”
Ask whether the person has relevant expertise and whether other qualified people agree. This overlaps with source evaluation, which looks at who is speaking and on what basis.
Appeal to emotion
Emotion is not out of place in an argument about things that matter, but it becomes a fallacy when it replaces reasons. Fear, pity, flattery and outrage can all be used to push a conclusion the evidence does not support.
Example: “Think of the children! Anyone who disagrees with this plan does not care.”
Notice when you are being told how to feel instead of what the facts are.
Circular reasoning
The conclusion is assumed in the premise.
Example: “This book is reliable because it says so in the introduction.”
The argument goes in a loop and adds nothing new. It can be hard to spot when the wording is varied.
Post hoc (false cause)
This assumes that because one event followed another, the first caused the second.
Example: “I wore my lucky socks and we won, so the socks work.”
Sequence is not causation. Other factors, chance and confounders all need to be ruled out, a theme covered in correlation and causation.
Hasty generalization
This draws a broad conclusion from too few or unrepresentative examples.
Example: “I met two rude people from that town, so everyone there must be rude.”
Ask how many cases there are, how they were chosen, and whether they represent the whole group.
Cherry-picking
Only the evidence that supports a point is shown, and the rest is left out.
Example: A report mentions the three months when sales rose, and omits the nine when they fell.
It is closely related to confirmation bias, since both involve selective attention to evidence.
Moving the goalposts
When the standard of proof is met, it is raised.
Example: “Show me one study.” Then, when one is shown: “One study doesn’t count. Show me ten.”
Sometimes a higher bar is fair, but if the requirement keeps changing, the person may not be open to evidence at all.
Tu quoque (“you too”)
This dismisses a criticism by pointing out that the critic does the same thing.
Example: “You tell me to save money, but you bought a new phone last month.”
Hypocrisy may be unflattering, but the advice can still be good.
Using this knowledge well
- Apply it first to yourself. It is easier to see fallacies in people you disagree with. Check your own arguments with the same standard.
- Ask for the reasoning, not a label. Saying “That’s a straw man” may end a conversation. Saying “I don’t think I said that; here is what I meant” may continue it.
- Do not assume a bad argument means a bad conclusion. The claim may still be true; it just needs better support. This “fallacy fallacy” is an easy trap.
- Look at the structure. Most of these patterns show up as a gap between the reasons given and the conclusion drawn. Asking “does this actually follow?” catches many of them.
Learning the names makes patterns easier to notice, but understanding why each fails matters more than memorizing a list. Along with awareness of cognitive biases, it forms a basic toolkit for reading arguments carefully, whether in the news, an advertisement or a heated conversation.