GENERAL RULES OR CANONS OF THE SYLLOGISM 39 



It is only when, as in the above examples, M is subject in both premisses 

 [i.e. in the third figure (i$9)] that its extension is explicitly thought of in 

 both, and so made an identical point of reference for 5 and P. There the 

 reason for having M distributed at least once is clear. 



If, however, M is predicate of two affirmative premisses (i.e. in the second 

 figure), the extension of M is, as a rule, not explicitly thought of at all in either 

 premiss. And if such premisses as &quot; P is M,&quot; &quot; S is M,&quot; &quot; Birds fly? &quot; Bats 

 fly? yield no conclusion as to whether or not &quot; S is P? &quot;Bats are birds? 

 the reason is &quot; that it does not follow, because the same predicate attaches to 

 two subjects, that these can be predicated one of the other &quot;. l It is not the 

 extension of M that is here thought of as the common point of reference for S 

 and P. But if the same predicate, M t is affirmed of one extreme and denied 

 of the other, these can be denied of each other ; and in thus requiring one 

 negative premiss we are distributing its predicate Af t so that &quot; for working 

 purposes &quot; 2 we may say of this form of syllogism too that its validity requires 

 &quot; distributed middle &quot;. 



Again, if P be predicated of M and M of 6* (as in the first figure) &quot; M 

 is P, S is M, .-. S is P&quot; M must be distributed in the major premiss : 

 &quot; unless P is connected necessarily and universally with J/, it is clear that 

 what is M need not be P &quot;. 3 



B (4). The violation of the second rule of quantity is called 

 the Fallacy of Illicit Process of the major, or of the minor, 

 or of both extremes, as the case may be. The reason of the 

 rule is plain enough. *$&quot; and P are related in the conclusion be 

 cause and in so far as they were related to M in the premisses. 

 Hence, we have no right to take S or P any more definitely in the 

 conclusion than they were used in the premisses : to refer to all 

 5, or to all P, in the conclusion, if the minor or major referred 

 only to some 5, or to some P, indefinitely. We cannot infer that 

 because All criminals are wicked and some Irishmen are criminals 

 therefore &quot;All Irishmen are wicked&quot;: to do so would involve 

 the fallacy of illicit minor \ but only that (&amp;lt; Some Irishmen are 

 wicked &quot;. Similarly, we cannot infer that because All Spaniards 

 speak Spanish and No natives of Maynooth are Spaniards^ there 

 fore No natives of Maynooth speak Spanish. The conclusion, here, 

 may be true, or it may not ; but, whether it is or not, it does not 

 follow from the premisses. For the major does not state that 

 there are no other people besides Spaniards who speak Spanish ; 

 there may be others : and among these others may be some 

 natives of Maynooth. In other words, the syllogism is invalid 

 on account of the fallacy of illicit major. The major extreme, 



1 JOSEPH, op. cit., p. 250. z ibid. 



3 ibid. The distribution of M in the fourth figure (159) needs no separate dis 

 cussion. 



