ERROR AND FALLACIES 311 



described as the &quot; converse fallacy of the accident &quot;. The examples, 

 too, by which the fallacy of the accident is usually illustrated, 

 fail to distinguish the latter from the fallacy we have just been 

 considering. 1 



(d) ACCIDENS. The precise nature of this fallacy &quot;-rra/oa 

 TO o-vv/3e@r)K6s,&quot; &quot;per accidens &quot; has not been clearly determined. 

 It appears to be the mistake of assuming that whatever is pre- 

 dicable of a subject is also predicable of its &quot;accidents,&quot; i.e. of 

 attributes that are not commensurate with that subject ; or, con 

 versely, that the &quot;accidents&quot; of a given predicate are also, and 

 equally with the latter, predicable of its subject. Here are some 

 of the examples and solutions offered by Aristotle. &quot; Do you 

 know Corsicus? Yes. Do you know the man approaching 

 you with his face muffled? No. But he is Corsicus, and 

 you said you knew him. &quot; To be &quot;a man approaching with 

 his face muffled,&quot; is an accident of Corsicus ; and it does not 

 follow that because Corsicus is known, this accidental state of him 

 is known. &quot; Six is a few ; and thirty-six is six times six ; there 

 fore thirty-six is a few.&quot; But it is accidental to thirty-six to be 

 regarded as a few groups ; hence though &quot; fewness &quot; may be pre 

 dicated about an accidental condition of thirty-six it cannot be 

 predicated of thirty-six itself. &quot; To call you an animal is to speak 

 the truth ; to call you an ass is to call you an animal ; therefore 

 to call you an ass is to speak the truth.&quot; The fallacy here lies 

 in the minor premiss, in the assumption that if &quot; animal &quot; can 

 be predicated about a given subject, &quot; ass,&quot; which is an accident 

 of this predicate, can likewise be predicated of it. (The species- 

 notion is always an accidens of the genus-notion : the fundamen- 

 tum divisionis must be an accidens of the genus : some animals are 

 asses, but an animal need not necessarily be an ass). Sometimes, 

 of course, a subject (or predicate) and one of its accidents may 

 be de facto commensurate. In such cases the fallacy does not 

 occur: we know from the subject-matter that the subject (or pre 

 dicate) may be validly replaced by its commensurate accident. 

 For instance, although the fallacy is committed in arguing that 

 all plane rectilinear figures have the sums of their interior angles 

 equal to two right angles, because this latter is true of all plane 

 triangles ; yet the fallacy is avoided in arguing that because all 

 right-angled triangles have the square on the hypotenuse equal 



1 Cf. JOSEPH, op. cit., p. 547 ; WELTON, op. cit., ii., p. 256 ; Palaestra Logica, 

 p. 86. 



