TERMS. 31 



class in general ; but it remains as a matter of important 

 consideration how far and in what manner we can safely 

 undertake thus to assign the place of objects in that 

 general system of classification which constitutes the 

 whole body of science. 



Twofold Meaning of General Names. 



EtymologicaUy the meaning of a name is what we are 

 caused to think of when the name is used. Now every 

 general name causes us to think of some one or more of 

 the objects belonging to a class ; it may also cause us to 

 think of the common qualities possessed by those objects. 

 A name is said to denote the distinct object of thought 

 to which it may be applied ; it implies at the same time 

 the possession of certain qualities or circumstances. The 

 number of objects denoted forms the extent of meaning 

 of the term ; the number of qualities implied forms 

 the intent of meaning. Crystal is the name of any sub- 

 stance of which the molecules are arranged in a regular 

 geometrical manner. The substances or objects in ques- 

 tion form the extent of meaning ; the circumstance of 

 having the molecules so arranged forms the intent of 

 meaning! 



When we compare a variety of general terms it may 

 often be found that the meaning of one is included in 

 the meaning of another. Thus all crystals are included 

 among material substances, and all opaque crystals are in- 

 cluded among crystals: here the inclusion is in extension. 

 We may also have inclusion of meaning in regard to 

 intension. For as all crystals are material substances, 

 the qualities implied by the term material substance 

 must be among those implied by crystal. Again, it is 

 obvious that while in extension of meaning opaque 

 crystals are but a part of crystals, in intension of meaning 



