Logical Fallacies

LogFall

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

Fallacy profile

Proof by example

Occurs when one or a few examples are offered as if they were enough to establish a universal claim.

ConceptualEvidential

Definition

Occurs when one or a few examples are offered as if they were enough to establish a universal claim.

Illustrative example

My friend used a chatbot to draft a great memo, so AI is clearly ready to replace analysts.

Teaching gauges

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

Recurring

60

Common in today's rhetoric

Common enough that most readers will meet it often.

Tricky

50

Easy to spot

Often hides inside wording, framing, or technical detail.

Very easy to slip into

80

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.

Quick check

Are the categories being used carefully, or are unlike things being treated as alike?

Why it misleads

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

Examples can illustrate a claim, but they do not by themselves prove a universal proposition. The missing question is whether the example is representative.

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

My friend used a chatbot to draft a great memo, so AI is clearly ready to replace analysts.

That's like saying...

That's like saying one swan on the lake proves every swan on earth is white. A few examples are being asked to do the work of a universal claim.

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 every time people disagree about definitions or categories. It applies when the category boundaries themselves are distorting the reasoning.

Use the label only when...

Use this label only when one or a few examples are offered as if they were enough to establish a universal claim. If the real problem is that the psychological or social effects of believing something are treated as evidence that the thing believed in actually exists or is true, the better label is Epistemic/ontological conflation.

Often confused with

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

Comparison

Epistemic/ontological conflation

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

Exact difference: Proof by example happens when one or a few examples are offered as if they were enough to establish a universal claim. Epistemic/ontological conflation happens when the psychological or social effects of believing something are treated as evidence that the thing believed in actually exists or is true.

Quick split: Are the categories being used carefully, or are unlike things being treated as alike? Then compare it with Are the categories being used carefully, or are unlike things being treated as alike?

Comparison

Appeal to nature

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

Exact difference: Proof by example happens when one or a few examples are offered as if they were enough to establish a universal claim. Appeal to nature happens when something is praised as good, safe, or right merely because it is called natural, or condemned as bad merely because it is called unnatural.

Quick split: Are the categories being used carefully, or are unlike things being treated as alike? Then compare it with Are the categories being used carefully, or are unlike things being treated as alike?

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

Proof by example threatens rationality because one or a few examples are offered as if they were enough to establish a universal claim.

Main reasoning problem

One or a few examples are offered as if they were enough to establish a universal claim.

Why this kind of mistake matters

It warps the conceptual map so that distinctions, boundaries, or levels of analysis mislead the inference.

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

Are the categories being used carefully, or are unlike things being treated as alike?

Prompt 2

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.

Google makes fixes to AI-generated search summaries after outlandish answers went viral

When AP covered Google's erroneous AI overviews, the central lesson was that a system can sound authoritative while still misreading queries, flattening context, or repeating bad source material. The episode is a strong real-world case of surface fluency masking evidential and conceptual weakness. The fallacy here is Proof by example: one or a few examples are offered as if they were enough to establish a universal claim. That matters here because examples can illustrate a claim, but they do not by themselves prove a universal proposition. A better analysis would remember that the missing question is whether the example is representative.

Associated Press · 2024-05-31

Researchers say an AI-powered transcription tool used in hospitals invents things no one ever said

AP's reporting on Whisper hallucinating in hospital transcripts is a sharp case of a polished output being treated as if accuracy followed from confidence and fluency. It also shows why one plausible-seeming example is not enough to certify a tool as reliable in high-stakes settings. The fallacy here is Proof by example: one or a few examples are offered as if they were enough to establish a universal claim. That matters here because examples can illustrate a claim, but they do not by themselves prove a universal proposition. A better analysis would remember that the missing question is whether the example is representative.

Associated Press · 2024-10-26

A single accurate prediction, one striking conversion story, or one dramatic crime clip is often treated as if it proved a broad thesis about markets, religion, or social decline. The fallacy here is Proof by example: one or a few examples are offered as if they were enough to establish a universal claim. That matters here because examples can illustrate a claim, but they do not by themselves prove a universal proposition. A better analysis would remember that the missing question is whether the example is representative.

Debates about AI often jump from one impressive demo or one embarrassing failure to a total conclusion about the technology as a whole. The fallacy here is Proof by example: one or a few examples are offered as if they were enough to establish a universal claim. That matters here because examples can illustrate a claim, but they do not by themselves prove a universal proposition. A better analysis would remember that the missing question is whether the example is representative.

Related fallacies

Nearby entries chosen by shared categories and family resemblance.