ويشترط في إنتاج الشكل الثاني بحسب الكيف أي: الإيجاب والسلب اختلاف المقدمتين
For the second figure to produce a conclusion, the premises must differ in quality: one affirmative, the other negative.
Quality means affirmation or negation; it is not the distinction between universal and particular. If the minor is affirmative, the major must be negative; if the minor is negative, the major must be affirmative.
Two affirmative premises, or two negative premises, leave the relation between the subjects undetermined even though both have the same middle predicate.