# Illicit major

*Also called: Illicit process of the major term*

- **Cluster:** Broken structure — The form itself does not carry the conclusion
- **Page:** https://fallacy.wiki/fallacy/illicit-major/
- **In Arabic:** https://fallacy.wiki/ar/fallacy/illicit-major.md
- **Licence:** CC BY 4.0 — https://creativecommons.org/licenses/by/4.0/

## What it is

Drawing a conclusion about all of a category from a premise that covered only part of it.

## In the wild

> All cats are mammals; no dogs are cats, so no dogs are mammals.

## How to answer it

Check whether the premise really covered every member of the term in the conclusion.

## Origin and naming

One of the two classic distribution errors in categorical syllogisms. 'Illicit' marks that the major term — the term in the conclusion's predicate — is claimed about its whole class in the conclusion even though the premises only talked about part of it. It is the structural twin of the illicit minor.

## More places it shows up

- All managers are accountable for the budget; no intern is a manager; so no intern is accountable for the budget — while interns sign for petty cash every week.
- All certified auditors may sign off on the report; she is not a certified auditor; so she may not sign — overlooking the partner who co-signs.
- All encryption keys are stored in the vault; this token is not an encryption key; so it is not in the vault — and it is.
- All senior staff have building access; contractors are not senior staff; so contractors can't enter the building — said at the door where they badge in daily.

## How to spot it

- Notice when the conclusion makes a sweeping 'no' or 'all' claim about a class the premises never fully covered.
- Notice when the pattern is 'all A are B; C is not A; so C is not B' — the shape alone should raise the flag.
- Notice when the conclusion excludes something from a class using premises that never said who else belongs to that class.

## Nearby

- [Undistributed middle](https://fallacy.wiki/fallacy/undistributed-middle.md)
- [Existential fallacy](https://fallacy.wiki/fallacy/existential.md)

## Read more

- [Wikipedia](https://en.wikipedia.org/wiki/Illicit_major)
- [Fallacies Online](https://fallacies.online/wiki/logic/formal_fallacies/fallacies_of_distribution/illicit_process)

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From fallacy.wiki — a bilingual field guide to 91 logical fallacies, published by phi holdings. Licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/): reuse freely with attribution to fallacy.wiki.