A-15. No motorcycles are limousines. All motorcycles are fast vehicles. So no fast vehicles are limousines.
以"M"表"中詞motorcycles "；"S"表"小詞fast vehicles "；"P"表"大詞limousines"
No motorcycles are limousines All motorcycles are fast vehicles ∴ No fast vehicles are limousines | 左邊論證的邏輯形式如右： | No M are P All M are S ∴ No S are P |
由簡化的論證形式可知，此論證的
mood是EAE
figure是figure3
此論證無效。
B-6. All friends of mine are people on the team. Some friends of mine are people 7 feet tall. So some people 7 feet tall are people on the team.
以"M"表"中詞friends of mine "；"S"表"小詞 people 7 feet tall"；
"P"表"大詞people on the team"
All friends of mine are people on the team Some friends of mine are people 7 feet tall ∴ Some people 7 feet tall are people on the team | 左邊論證的邏輯形式如右： | All M are P Some M are S ∴ Some S are P |
由簡化的論證形式可知，此論證的
mood是AII
figure是figure3
依照大、小兩前提可畫出此論證的范恩圖，可從左圖得知，S與P交集的部份有一定不是空集合的部份，因此可導出「有些S不是P」。所以這是有效論證。
