註：



This argument is in the form of :







Major Premise: Only S is P and only P is S （both sufficient and necessary condition)



Minor Premise: Q is not p



Conclusion: Q is, therefore, not S







(*The content of the argument has nothing to do with validity of the form of the argument.)



- See more at: http://blog.creaders.net/ChinaPhilosopher/user_blog_diary.php?did=225250#sthash.Q8w2WF3w.dpuf





Valid syllogistic forms



In syllogistic logic, there are 256 possible ways to construct categorical syllogisms using the A, E, I, and O statement forms in the square of opposition. Of the 256, only 24 are valid forms. Of the 24 valid forms, 15 are unconditionally valid, and 9 are conditionally valid.



F1 F2   F3 F4

Barbara Cesare   Datisi Calemes

Celarent Camestres Disamis Dimatis

Darii Festino   Ferison Fresison

Ferio Baroco   Bocardo Calemos

Barbari Cesaro   Felapton Fesapo

Celaront Camestros Darapti Bamalip



Unconditionally valid (15)

Figure 1

AAA

EAE

AII

EIO



Figure 2

EAE

AEE

EIO

AOO



Figure 3

IAI

AII

OAO

EIO



Figure 4

AEE

IAI

EIO



Conditionally valid (9)



Figure 1

AAI

EAO



Figure 2

AEO

EAO



Figure 3

AEO S exists

AAI

EAO



Figure 4

EAO M exists

AAI P exists