Unwarranted Contrast
The fallacy of assuming that conversational implicature (what is suggested in everyday speech) is a logical implication (what must be true). For instance, saying 'some are' does not logically guarantee 'some are not', even though it is often implied.
THE IDEA
Unwarranted Contrast
(also known as: some are/some are not)
Description: Assuming that implicature means implication, when it logically does not. Implicature is a relation between the fact that someone makes a statement and a proposition. Implication is a relation between propositions, that is, the meanings of statements.
Logical Form: Person 1 makes statement X. Therefore, it is logically implied that Y.
Example #1: "Some people are humanitarians." Therefore, some people are not humanitarians.
Explanation: This might be the case, but we cannot logically infer that this is the case, because the use of “some” does not logically imply that it does not mean “all”. In everyday use, “some” does implicate “not all”, that is why this is fallacious and could be used to deceive without technically lying.
Example #2: "Some Christians are not Jews." Therefore, some Christians are Jews.
Explanation: Just because we stated that some Christians are not Jews, does not mean we can logically conclude that some Christians are Jews. While we may implicate it, the statement does not imply it.
Exception: None.
When to use it
Detecting deceptive advertising that claims 'some dermatologists recommend X' to imply the rest do not.
Evaluating a statement such as 'Some of my opponents are corrupt' without inferring that the remaining opponents are necessarily honest.
Improving logical rigor in legal arguments where 'some evidence suggests...' must be carefully distinguished from 'the evidence implies...'.
Analyzing survey results to avoid drawing negative conclusions about the population not mentioned in a positive statistic.
FROM THEORY TO EVERYDAY LIFE
In practice
Example #1: Humanitarians
The statement 'Some people are humanitarians' is used to imply that some people are not humanitarians. This is a conversational implicature, but not a logical necessity. It is fallacious to treat it as a logical conclusion.
Example #2: Christians and Jews
The statement 'Some Christians are not Jews' might be intended to implicate that some Christians are Jews, but this is not logically implied by the statement.
A MOMENT TO REFLECT
Put it to work.
When you hear someone say 'some people are...', do you automatically assume they mean 'but not all'? How can you check whether 'all' actually applies?
In what types of arguments (e.g., legal, marketing, political) is the Unwarranted Contrast fallacy most likely to be deceptive?
How does understanding the difference between implicature and implication change the way you read statistical claims like 'Most of the group agreed'?
CONTINUE THE CONVERSATION
Source texts
- Logically Fallacious - The Ultimate Collection of Over 300 Logical Fallacies