Syllogistic Rules

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1. The middle term must be distributed at least once.
    Error is the fallacy of the undistributed middle.
2. If a term is distributed in the CONCLUSION, then it must be distributed in a premise.
    Error in the subject is the fallacy of the undistributed minor;
    error in the predicate is the fallacy of the undistributed major.
3. Two negative premises are not allowed.
    Error is the fallacy of exclusive premises.
4. A negative premise requires a negative conclusion; and conversely.
    Error is the fallacy of drawing an affirmative conclusion from negative premises; or
    error is the fallacy of drawing a negative conclusion from affirmative premises.
5. If both premises are universal, then the conclusion must be universal. (Holds for arguments based on modern logic, and for Aristotlean arguments concerning nonexistent things.)
    Error is the existential fallacy.