What a fallacy is
A fallacy is a flaw in reasoning: the conclusion does not follow properly from the reasons given. Fallacies can be hard to notice because they often sound persuasive. Some are accidental, and some are used on purpose, but the same test applies to both: even if every statement is true, does the conclusion actually follow?
Two cautions before the list. First, an argument with a fallacy can still have a true conclusion. The flaw only means the argument does not establish it. Second, the names below are descriptive tools, and they work best as questions to ask rather than accusations to throw.
Fallacies about the person
Ad hominem
This attacks the person instead of the argument. “You can’t trust her view on budgeting; she once got into debt.” The person’s history may be worth knowing, but the argument still has to be judged on its own terms. A related version points to someone’s motives to dismiss the claim without addressing it.
Context matters. Pointing out that a source has a financial interest can be fair when evaluating trust, as long as you do not treat that as proof the claim is false.
Appeal to authority
Experts deserve weight, and relying on them is often sensible. The problem arises when the “authority” is outside their field, when experts in the field disagree, or when a name is offered in place of any reasoning. “A famous actor says this supplement works” is the familiar example.
Fallacies about the argument’s shape
Straw man
A straw man misstates someone’s position in a weaker form and then attacks that. If someone says they would like more bike lanes and the reply is “so you want to ban cars,” the reply has replaced the real view with an easier target.
False dilemma
This presents two options as if they were the only ones. “Either we ban all of it, or we accept all of it.” Real choices usually include middle ground, so whenever you see exactly two choices, ask what is missing.
Slippery slope
The claim is that one small step will inevitably lead to an extreme outcome, without showing why. Some chains of events are real, so the problem is not the idea of consequences but the lack of evidence for each link. A good reply is to ask what makes each step likely.
Circular reasoning
Here the conclusion is hidden in the premise. “This newspaper is reliable because it says so.” The reasoning goes in a loop and never offers outside support.
Fallacies about evidence
Hasty generalization
This draws a broad conclusion from a few examples. “I met two rude people from that city, so everyone there is rude.” Small, unrepresentative samples are a recurring problem, and they also connect to how reading statistics can go wrong.
Post hoc reasoning
The phrase means “after this, therefore because of this.” Something happened after something else, so the first is assumed to have caused the second. A person wears a certain shirt and their team wins; that does not make the shirt matter. The same confusion underlies mistakes about correlation and causation.
Cherry-picking
Cherry-picking means selecting only the examples that support a view and ignoring the rest. It can be deliberate or simply the result of noticing what we already agree with. Asking “what would the other side’s best evidence be?” helps counter it.
Appeal to popularity
“Everyone believes it, so it must be true.” Many people can be wrong together, and many people can also be right, so popularity alone says little about accuracy.
Fallacies about emotion and attention
Appeal to emotion
Feelings are legitimate, and emotions can reasonably tell us what matters. The fallacy occurs when strong emotion is used in place of evidence, such as a dramatic story offered as if it proved a general rule.
Red herring
This introduces an unrelated topic to change the subject. If you ask a politician about a budget and they reply about a rival’s past statements, the question has not been answered.
Tu quoque
Meaning “you too,” this deflects criticism by pointing out that the critic does the same. “You say I shouldn’t do that, but you do it as well.” Hypocrisy may be real, but it does not make the original point wrong.
Using this knowledge well
Learning these names can help you describe what feels off about an argument, but a few habits keep it useful:
- Aim at your own reasoning first. It is easier to see fallacies in people you disagree with, so check your own arguments for the same patterns.
- Be charitable. Before labeling something a straw man, check whether you have understood the position correctly.
- Do not stop at the label. Naming a fallacy is the beginning of the response, not the end. Explain what is missing, and remember that the conclusion could still be true.
- Watch for the “fallacy fallacy.” Assuming a conclusion is false merely because the argument for it was flawed is itself a reasoning error.
In ordinary conversation, many arguments are loose rather than strictly fallacious. People speak quickly and imperfectly, and a polite question like “What makes you think that follows?” usually does more good than a technical term.