Minor: No cat is a bird.
Major: No dog is a bird.
Both merely place cats and dogs outside the class of birds. Classes excluded from the same class may overlap or be entirely separate.
The premises do not establish a relation between cats and dogs. Two negative premises cannot determine how the minor and major terms relate.
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The Second Figure: Conditions of Validity and Four Productive Moods
Minor: No cat is a bird.
Major: No dog is a bird.
Both merely place cats and dogs outside the class of birds. Classes excluded from the same class may overlap or be entirely separate.
The premises do not establish a relation between cats and dogs. Two negative premises cannot determine how the minor and major terms relate.