The fallacies in this section are all cases of invalid categorical syllogisms. The fallacy is committed when a standard form categorical syllogism contains four terms.
All dogs are animals, and all cats are mammals, so all dogs are mammals.
While the same word is used, the word has different meanings , and hence the word is treated as two different terms. Only man is born free, and no women are men, therefore, no women are born free. The middle term in the premises of a standard form categorical syllogism never refers to all of the members of the category it describes. All Russians were revolutionists, and all anarchists were revolutionist, therefore, all anarchists were Russians. The middle term is 'revolutionist'.