CATEGORICAL JUDGMENTS AND PROPOSITIONS 237 



&quot;accidental,&quot; &quot;per accidens&quot; because &quot; the relation of a predicate 

 to its subject may be either accidental or essential. It must at least 

 be accidental, and therefore from its bare form we are entitled to 

 convert an A proposition as if P were an accident of 5 / but we 

 are not entitled to do more . . . if P is an accident of 5, i.e. 

 coincides in the same individual subject with 5, then 5 is pre- 

 dicable of a subject which P characterizes, and we may say that 

 some/MsS.&quot; 1 



The conversion of an A proposition without limitation or de 

 pression of the quantity, is one of the commonest of all fallacies ; 

 and it is particularly liable to be incurred in dealing with in- 

 designate propositions (96). Thus, it is wrongly inferred that 

 because clever people have large brains all who have large brains 

 are clever; that because idlers are commonly out of work all 

 unemployed people are idlers ; that because pious people go to 

 church all church-going people are pious; that because all 

 beautiful things are agreeable all agreeable things are beautiful. 2 



Of course, in some cases the universal (i.e. simple) converse of 

 an A proposition may be true : when the latter is a reciprocal pro 

 position, i.e. one in which 5 and P agree in connotation and in de 

 notation ; but we cannot know or infer this from the information 

 given us by the form of the convertend : we must know it 

 otherwise. The proposition &quot; All equilateral triangles are 

 equiangular,&quot; though true, cannot be formally inferred from 

 &quot;All equiangular triangles are equilateral &quot;. Were we givefi the 

 U proposition (105, 108), &quot;All equiangular triangles are all 

 equilateral triangles,&quot; we should have the proposition &quot;All equi- 



1 JOSEPH, op. cit., p. 212 (we have changed the symbols X and F, used by the 

 author). He adds the following important and instructive note: &quot; Even when the 

 predicate is known to be of the essence of the subject, we must convert per accidens 

 if the predicate is the genus : e.g. &quot; all men are animals &quot; &quot; some animals are men &quot;. 

 We cannot call animal an accident of man, but we may say that it is an accident 

 that an animal should be a man, in this sense, that the conditions necessary to the 

 generation of an animal must coincide with the conditions necessary for the genera 

 tion of a man, if the animal is to be a man. The expression coincide is not strictly 

 suitable (nor therefore can the relation of man to animal be strictly called accidental), 

 because it is only in thought that the conditions necessary to the generation of an 

 animal can be separated from the special conditions necessary for the generation of 

 some particular species : there is no coincidence of independent series, as when one 

 series of events brings a train to a point whither another series has brought a flood 

 and washed away the metals, and the result is a railway accident.&quot; But the usage 

 is analogous in both cases. Their consideration will recur in connexion with the 

 concept of chance (264) and with the fallacy of the Accident (274, d). 



2 WELTON, op. cit., p. 257 ; MELONB, op. cit., p. 83. 



