74 THE SCIENCE OF LOGIC. 



which the subject has in common with other classes of things (the 

 pars determinabilis naturae], or (3) the part which differentiates 

 the subject from all other classes of things (the pars determinans 

 naturae}. In the latter case the predicate must give us (4) either 

 something which, though not regarded as essential to the subject 

 or a part of its nature, is nevertheless necessarily connected with 

 that nature ; or (5) finally, it will give us something not necessarily, 

 but only contingently, accidentally and de facto conjoined or co 

 incident with that nature. There is no other possible alternative. 

 Hence, in every logical judgment which affirms a relation between 

 two concepts, subject and predicate : 



the predicate must 

 be either a 



1. species ( 



2. genus (761/05) 



3. differentia 



4. proprium (i&iov) or 

 .5. accidens 



, of the subject. 



It will be noted that the results are here reached by examining 

 relations of intension, which we know already to be more funda 

 mental in our concepts than their extension. 



Comparing our ideas from the point of view of their extension, 

 we find (a) that the predicate of a proposition may give exactly 

 a whole class coextensive with the subject-class, either (i) in 

 virtue of its giving the whole connotation of the latter (species), 

 or (2) the differentiating portion of it (differentia), or (3) a pro 

 perty necessarily connected with its connotation (proprium) ; or 

 (b) that the predicate may give a wider class to which the subject 

 belongs, either (4) by giving the common portion of the connota 

 tion of the latter (genus], or (5) some other attribute not neces 

 sarily connected with the connotation of the subject, but which 

 the latter happens to possess, and which makes it a part or sub 

 class of this wider class (accidens]. 



It must not be forgotten that those various objective concepts 

 (or objects of our concepts), which we distinguish mentally from one 

 another, and between . which we apprehend the various relations 

 of genus, differentia, species, proprium, and accidens, are not so 

 many really and numerically distinct entities composing any 

 really existing individual thing, as stones compose a heap, or as 

 words are in a book, or as the various organs are in the human 

 body : the individual is one existing reality : the mind, by the 

 process of abstraction (2), analyses, or breaks up, or distinguishes 



