402 THE SCIENCE OF LOGIC 



the universal premiss without having encountered and examined 

 the conclusion in that very process. 



Now if that were so y if it were always necessary to meet and 

 examine every individual case under a universal principle be 

 fore formulating this principle and assenting to it with certitude, 

 then, undoubtedly, every syllogism would be a petitio principii. 

 Having such a &quot;universal&quot; as its major premiss, and some par 

 ticular case under this &quot;universal&quot; as conclusion, it would clearly 

 be a petitio pri ncipii, if put forward as a proof of this conclusion. 

 In fact, such a syllogism would not be a real inference at all. 

 There are cases in which &quot; universal &quot; judgments are formed 

 in the way indicated, by a complete enumeration of instances ; 

 and it will be freely admitted that wherever our universal pre 

 miss is a mzrz collective universal (92, a, i) comprising a concrete, 

 limited class, and is reached by an enumeration of all the par 

 ticular facts or instances that constitute it, while our conclusion 

 refers to one or more of these facts or instances, though we 

 have indeed the form of a syllogism, we have neither proof nor 

 inference?- Take the following examples of apparent syllogisms 

 with enumerative universals as major premisses : &quot; All the apostles 

 were Jews ; Judas was an Apostle ; therefore he was a Jew &quot;. 

 &quot; All the books on this shelf treat of logic ; this is one of them ; 

 therefore it treats of logic &quot;. &quot; All the known planets move in 

 elliptical orbits around the sun ; the earth is one of the known 

 planets ; therefore it moves in an elliptical orbit around the sun &quot;. 

 &quot;All the days of the week are called after pagan deities ; Monday 

 is a day of the week ; therefore it is called after a pagan deity &quot;. 

 These have the outward form of syllogisms. They are in fact 

 not inferences at all ; and, if advanced as proofs of their respective 

 conclusions, they do involve the fallacy of petitio principii : the 

 enumerative majors could not be known to be true unless the 

 conclusions were antecedently or simultaneously known to be 

 true : for in each case it was by an examination of all the in 

 dividual instances (including the conclusion) that the truth about 

 the whole concrete collection was reached. 



1 A collective universal major may afford a real inference to one who has learned 

 its truth otherwise than by an enumeration of its members. The minor, in such a 

 case, gives real information not contained in his knowledge of the major : &quot; If I 

 learn that the vessel XY was lost at sea with all on board, and learn subsequently, 

 or by some other means, that my friend AB was a passenger on that vessel, then there 

 is no doubt that the conclusion is something new, although the major states a 

 mere collective fact, which (for those who know, but not for me) already contains 

 the conclusion.&quot; MELLONE, Logic, p. 231. 



