Fallacy of Every and All

Description: When an argument contains both universal quantifiers and existential quantifiers (all, some, none, every) with different meanings when the order of the quantifiers is reversed. This is a specific form of equivocation.

Example #1:

Everyone should do something nice for someone. I am someone, so do something nice for me!

Explanation: Assuming one accepts the premise that "everyone should do something nice for someone," the word "someone" in that sentence means "some person or another" whereas in the second sentence it means "a specific person." By equivocating the meanings of "someone," we appear to be making a strong argument when in fact we are not.

Example #2:

The sign reads, "All kids eat for free on Tuesdays!" Today is Tuesday, and there are many kids in the world not eating for free. Therefore, the sign is full of crap.

Explanation: The meaning of "all" on the sign is "no kid will be excluded from the offer." In the second sentence, the word "all" means "every kid in the world is not accepting the offer."

References: {apa}

Salmon, M. H. (2012). Introduction to Logic and Critical Thinking. Cengage Learning.


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