Logical Fallacies

LogFall

A practical logical-fallacies reference with clear explanations, usable examples, and teaching tools.

Fallacy profile

Argument from ignorance

Occurs when someone concludes that a claim is true because it has not been disproved, or false because it has not been proved.

Evidential

Definition

Occurs when someone concludes that a claim is true because it has not been disproved, or false because it has not been proved.

Illustrative example

No one has proved that the leaked memo is fake, so it is probably genuine.

Teaching gauges

These 0-100 gauges are teaching aids for comparing fallacies. They are editorial classroom estimates, not measured statistics.

Very common

70

Common in today's rhetoric

Appears regularly in everyday public rhetoric.

Moderate

55

Easy to spot

Recognizable, but easy to miss in a fast or heated exchange.

Very easy to slip into

75

Easy to innocently commit

A frequent unintentional slip in ordinary reasoning.

Foundational

25

Difficulty

Usually approachable without much prior logic background.

Middle school+Scientific reasoning

Reference

Family

Evidential/Methodological Fallacy

The mistake lies in how evidence is gathered, weighed, interpreted, or treated as sufficient.

Aliases

appeal to ignorance

Quick check

What evidence is missing, selected, or overstretched here?

Why it misleads

A fuller explanation of how the fallacy works and why it can look persuasive.

The burden is not met by pointing to a gap in refutation. A claim needs positive support of its own. Lack of an explanation is not the same thing as evidence for a preferred explanation.

That's like saying...

Instead of leading with the label, this analogy answers the shape of the reasoning move directly so the mistake is easier to see in plain language.

Fallacious claim

No one has proved that the leaked memo is fake, so it is probably genuine.

That's like saying...

That's like saying the locked room must contain treasure because nobody has opened the door yet. Lack of disproof is not the same thing as proof.

Caveat

This label is easy to overuse. The point here is not to call every weak argument by this name, but to reserve it for the exact misstep it describes.

Common misapplication

Do not use this label simply because the evidence is incomplete. It applies when the argument claims more support than the evidence has actually earned.

Use the label only when...

Use this label only when someone concludes that a claim is true because it has not been disproved, or false because it has not been proved. If the real problem is that someone treats a failure to find expected evidence as if it counted for nothing against the claim, even in a context where the claim should leave detectable traces, the better label is Absence of evidence fallacy.

Often confused with

These near neighbors are easy to mix up, so use the comparison to see the exact difference.

Comparison

Absence of evidence fallacy

Why people mix them up: Both often look like evidential mistakes at first glance.

Exact difference: Argument from ignorance happens when someone concludes that a claim is true because it has not been disproved, or false because it has not been proved. Absence of evidence fallacy happens when someone treats a failure to find expected evidence as if it counted for nothing against the claim, even in a context where the claim should leave detectable traces.

Quick split: What evidence is missing, selected, or overstretched here? Then compare it with What evidence is missing, selected, or overstretched here?

Comparison

Argument from fallacy

Why people mix them up: Both often look like evidential mistakes at first glance.

Exact difference: Argument from ignorance happens when someone concludes that a claim is true because it has not been disproved, or false because it has not been proved. Argument from fallacy happens when someone infers that because a particular argument for a conclusion is weak or fallacious, the conclusion itself must therefore be false.

Quick split: What evidence is missing, selected, or overstretched here? Then compare it with What evidence is missing, selected, or overstretched here?

Practice And Repair

Extra teaching tools that show why the fallacy is persuasive, what to look for, and how to correct it.

Why it matters

Why this mistake matters

Argument from ignorance threatens rationality because someone concludes that a claim is true because it has not been disproved, or false because it has not been proved.

Main reasoning problem

Someone concludes that a claim is true because it has not been disproved, or false because it has not been proved.

Why this kind of mistake matters

It overstates, understates, cherry-picks, or misallocates the force of evidence.

Check yourself

The assessment area now uses mixed 10-question sets, so the fallacy is not announced in the title before the quiz begins.

What the assessment does

You will work through a mixed set of fallacy-identification questions. Focused links from a fallacy page will quietly include this fallacy among nearby look-alikes without announcing the answer in the page title.

Questions to ask

Use these category-based prompts to audit similar arguments.

Prompt 1

What evidence is missing, selected, or overstretched here?

Case studies

Each case study explains why the example fits the fallacy and links back to its source whenever source information is available.

Pentagon study finds no sign of alien life in reported UFO sightings going back decades

AP's March 8, 2024 report on the Pentagon's UFO review is a textbook reminder that 'not fully explained' does not mean 'therefore alien' or 'therefore conspiracy.' The remaining uncertainty in the file is exactly what makes the episode useful for thinking about overconfident belief formation. The fallacy here is Argument from ignorance: someone concludes that a claim is true because it has not been disproved, or false because it has not been proved. That matters here because the burden is not met by pointing to a gap in refutation. A better analysis would remember that a claim needs positive support of its own.

Associated Press · 2024-03-08

New Pentagon report on UFOs includes hundreds of new incidents but no evidence of aliens

AP's November 14, 2024 story on hundreds of new UAP reports is a useful case because it mixes explained incidents, unexplained incidents, and limited data without pretending they all support the same conclusion. It is exactly the kind of evidence landscape that invites cherry-picking and premature certainty. The fallacy here is Argument from ignorance: someone concludes that a claim is true because it has not been disproved, or false because it has not been proved. That matters here because the burden is not met by pointing to a gap in refutation. A better analysis would remember that a claim needs positive support of its own.

Associated Press · 2024-11-14

How an unsubstantiated, anonymous affidavit about the ABC presidential debate was amplified online

PolitiFact's September 20, 2024 reconstruction of the fake ABC whistleblower affidavit is especially valuable because it shows how public figures shared the claim while conceding they did not know whether it was true. That is a live, well-documented case of conjecture and amplification outrunning authentication. The fallacy here is Argument from ignorance: someone concludes that a claim is true because it has not been disproved, or false because it has not been proved. That matters here because the burden is not met by pointing to a gap in refutation. A better analysis would remember that a claim needs positive support of its own.

PolitiFact · 2024-09-20

After an anonymous affidavit circulated online in September 2024 alleging that ABC had secretly rigged the Harris-Trump debate, many posts treated the absence of immediate disproof as if it were evidence that the allegation was real. The fallacy here is Argument from ignorance: someone concludes that a claim is true because it has not been disproved, or false because it has not been proved. That matters here because the burden is not met by pointing to a gap in refutation. A better analysis would remember that a claim needs positive support of its own.

UAP discussions often jump from 'we do not yet know what caused this' to 'therefore it was extraterrestrial technology,' which treats unexplained as if it meant explained by the favored hypothesis. The fallacy here is Argument from ignorance: someone concludes that a claim is true because it has not been disproved, or false because it has not been proved. That matters here because the burden is not met by pointing to a gap in refutation. A better analysis would remember that a claim needs positive support of its own.

Related fallacies

Nearby entries chosen by shared categories and family resemblance.