Logical Fallacies and Cognitive Biases, Explained

Common fallacies to start with

The patterns most people meet first. Each links to a full entry with an example, a look-alike that is not a fallacy, and a fix.

Straw Man

Replacing someone's argument with a weaker version, then knocking down the weaker version.

Ad Hominem

Attacking the person making an argument instead of the argument itself.

False Dichotomy

Framing a choice as two options when more exist.

Slippery Slope

Claiming a small step will inevitably cause a chain of extreme consequences, without showing why.

Red Herring

Introducing an irrelevant topic to distract from the actual argument.

Appeal to Authority

Using a person's status as proof of a claim, instead of the evidence behind the claim.

Whataboutism

Deflecting a criticism by raising a different criticism of the critic or their side.

Confirmation Bias

The tendency to notice, remember, and trust evidence that supports what you already believe.

Sunk Cost Fallacy

Continuing a course of action because of what has already been spent on it, rather than what it still offers.

Moving the Goalposts

Dismissing evidence that meets your demand, then demanding new, harder evidence.

Motte and Bailey

Defending a bold claim by retreating to a weaker, related claim when challenged, then returning to the bold claim later.

Correlation Is Not Causation

Treating a statistical association as evidence of cause without ruling out confounders, reverse causation, selection, or chance.

All 63 logical fallacies and biases, with definitions

Browse by category

Logical fallacies 28

Errors in reasoning that make an argument invalid or misleading, regardless of the conclusion.

Cognitive biases 9

Predictable patterns in how the mind distorts judgment. Useful to name, hard to avoid.

Rhetorical devices 9

Techniques used to persuade rather than reason. Some are fair; many are traps.

Debate tactics 7

Moves people make in arguments: dodges, traps, and bad-faith patterns worth naming.

Statistical fallacies 10

Errors in reading data and evidence: samples, averages, correlations, and what the numbers do not say.

Find one by what happened

You can only cite a fallacy once you know what it is called. Start from the description instead.

What fallacy is this? See every description

What a logical fallacy is

A logical fallacy is a flaw in the structure of an argument. The conclusion does not follow from the reasons given for it. The conclusion may still be true. A fallacy only tells you that this argument does not get you there.

Most are easy to commit and hard to notice from the inside, which is why they have names. The straw man, the false dichotomy, and the slippery slope turn up in everyday arguments far more often than in logic textbooks.

Logical fallacy vs cognitive bias

A cognitive bias is not an argument. It is a predictable tilt in how people weigh evidence: noticing what confirms a belief (confirmation bias), or refusing to walk away from what has already been spent (sunk cost). Biases explain why fallacies feel convincing. Everyone has them, including the person pointing one out.

What each entry covers

Every page has the same five parts: the idea in plain terms, why the reasoning fails, a realistic example, a look-alike case that is not a fallacy, and how to fix the argument. The last two are the point. Most people arrive because someone sent them a link, and a way to say it better is more use than a list of things not to do.