Illicit Major
A formal logical fallacy in categorical syllogisms where the major term is distributed in the conclusion but not in the major premise.
THE IDEA
Illicit Major
(also known as: illicit process of the major term)
Description: Any form of a categorical syllogism in which the major term is distributed in the conclusion, but not in the major premise.
Logical Form:
- Premise 1: All A are B.
- Premise 2: No C are A.
- Therefore, No C are B.
Example #1:
- All healthy options are fast food.
- No salads are healthy options.
- Therefore, no salads are fast food.
Explanation: In our example, the major term is “fast food”, because it is the term that appears in the major premise (first premise) as the predicate, and in the conclusion. As such, in this position, it is “undistributed” in the premise but distributed in the conclusion.
Example #2:
- All comedians are hilarious.
- No teachers are comedians.
- Therefore, no teachers are hilarious.
Explanation: In our example, the major term is “hilarious”, because it is the term that appears in the major premise (first premise) as the predicate, and in the conclusion. As such, in this position, it is “undistributed” in the premise but distributed in the conclusion.
Exception: None.
When to use it
Evaluating the formal validity of deductive arguments in logic or mathematics.
Checking for overgeneralization or flawed category logic in policy debates.
Analyzing categorical statements in legal arguments or scientific classifications.
Preparing for standardized tests that assess logical reasoning skills (e.g., LSAT).
FROM THEORY TO EVERYDAY LIFE
In practice
Fast Food and Health
- All healthy options are fast food.
- No salads are healthy options.
- Therefore, no salads are fast food.
Explanation: The major term is 'fast food'. In the major premise (All healthy options are fast food), 'fast food' is not distributed. In the conclusion (No salads are fast food), 'fast food' is distributed. This shift makes the argument an Illicit Major fallacy.
Comedians and Hilarity
- All comedians are hilarious.
- No teachers are comedians.
- Therefore, no teachers are hilarious.
Explanation: The major term is 'hilarious'. In the major premise (All comedians are hilarious), 'hilarious' is not distributed. In the conclusion (No teachers are hilarious), 'hilarious' is distributed. This is an Illicit Major fallacy.
A MOMENT TO REFLECT
Put it to work.
Why can a conclusion not make a claim about every member of a class when the premises have not established it?
Can you construct a real-world argument that accidentally commits the Illicit Major fallacy?
How does understanding the technical concept of 'distribution' help avoid this fallacy when constructing or critiquing reasoning?
CONTINUE THE CONVERSATION
Source texts
- Logically Fallacious - The Ultimate Collection of Over 300 Logical Fallacies