| Fallacy of the Four Terms (quaternio terminorum) | A standard form categorical syllogism contains four terms. |
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| Examples: | |
| (i) All dogs are animals, and all cats are mammals, so all dogs are mammals. The four terms are: dogs, animals, cats and mammals. | |
| Note: In many cases, the fallacy of four terms is a special case of equivocation. While the same word is used, the word has different meanings, and hence the word is treated as two different terms. | |
| Consider the following example: | |
| (ii) Only man is born free, and no women are men, therefore, no women are born free. | |
| The four terms are: man (in the sense of 'humanity'), man (in the sense of 'male'), women and born free. | |
| Proof: | |
| Identify the four terms and where necessary state the meaning of each term. | |