fallacy of illicit major premise
Quick Summary
The fallacy of the illicit major premise occurs in formal logic when a term that is undistributed in the premise becomes distributed in the conclusion. A term is distributed when a proposition refers to all members of the class that the term denotes.12
In a syllogism, if the major term (the predicate of the conclusion) is distributed in the conclusion but not in the premise, the argument commits the fallacy of the illicit major premise. For example, the argument "All tubers are high-starch foods; no squashes are tubers; therefore, no squashes are high-starch foods" is fallacious because "high-starch foods" is distributed in the conclusion but not in the premise.1
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