What is the existential fallacy?

• A. Inferring a universal conclusion from particular premises
• B. Inferring the negation of a term from the premises
• C. Inferring a particular conclusion from universal premises
• D. Inferring that two terms are identical

Answer: (C)

The existential fallacy is when you move from universal statements to a claim that something exists. In other words, you infer a particular conclusion (there exists at least one S that is P) from premises that only assert universals (All S are P or No S are P) and don’t guarantee any member of S exists.

For example, if you have All unicorns are white, you cannot conclude that some unicorn exists. So concluding “There exists a unicorn that is white” commits the existential fallacy. Likewise, from All dogs are mammals and All mammals are animals, concluding Some dog is an animal asserts existence from only universal premises, which is not justified. This is exactly why inferring a particular conclusion from universal premises is the hallmark of the existential fallacy.