422 PROCEEDINGS OF THE AMERICAN ACADEMY 



sum of real external attributes (Shedden, Spalding, Devey, De Mor- 

 gan, Jevons, McGregor, Fowler). 



According to most writers, comprehension consists of the (necessary) 

 attributes thought as common to the objects. Shedden defines it as 

 consisting of all the attributes common to the things denoted. 



Again, most logicians consider as marks only such as are virtually * 

 predicated ; a few, perhaps, only such as are actually thought, and still 

 fewer include those which are habitually thought. Here and there is 

 found an author who makes comprehension include all true attributes, 

 whether thought or not. 



There is also a difference in the mode of reckoning up the marks. 

 Most writers count all distinguishable marks, while a few consider co- 

 extensive marks as the same. 



In the use of the term " extension " the want of a definite convention is 

 still more marked. The Port Royalists define it as " those subjects 

 to which the idea applies." It would appear, therefore, that it might 

 include mere fictions. 



Others limit the term to real species, and at the same time extend it 

 to single beings. This is the case with Watts, and also with Friedrich 

 Fischer. 



Others are most emphatic in declaring that they mean by it things, 

 and not species, real or imaginary. This is the case with Bachmann, 

 Esser, and Schulze. 



Others make it include neither concepts nor things, but singular 

 representations. This is the case with the strict Kantian. 



The following table exhibits this diversity : — 



Extension embraces 



Individual representations according to Kant, E. Reiuhold, etc. 



Representations " " Fries,. Uberweg, etc. 



Real external things and species " " Watts, Shedden, etc. 



Real external individual objects " " Bachmann, Devey, etc. 



Things " " Schulze, Bowen, etc. 



Species " " Drobisch, De Morgan, etc. 



Objects (representations) " " Thomson, etc. 



Individuals " " Mahan. 



Concepts " " Herbart, Vorlander, etc. 



General terms " " Spalding. 



Psychical concepts " " Strumpell. 



Variable marks " Bitter. 



* I adopt the admirable distinction of Scotus between actual, habitual, and vir- 

 tual cognition. 



