308 OPERATIONS SUBSIDIARY TO INDUCTION. 



many of the received opinions respecting the use of 

 definitions, and the nature of scientific propositions, 

 that they will probably appear to many persons highly 

 illogical and unphilosophical. But a disposition to 

 such a judgment arises in a great measure from this, 

 that the mathematical and mathematico-physical sci- 

 ences have, in a great degree, determined men's views 

 of the general nature and form of scientific truth; 

 while Natural History has not yet had time or oppor- 

 tunity to exert its due influence upon the current 

 habits of philosophizing. The apparent indefiniteness 

 and inconsistency of the classifications and definitions 

 of Natural History belongs, in a far higher degree, to 

 all other except mathematical speculations ; and the 

 modes in which approximations to exact distinctions 

 and general truths have been made in Natural History, 

 may be worthy our attention, even for the light they 

 throw upon the best modes of pursuing truth of all 

 kinds." 



" Though in a Natural group of objects a definition 

 can no longer be of any use as a regulative principle, 

 classes are not therefore left quite loose, without any 

 certain standard or guide. The class is steadily fixed, 

 though not precisely limited; it is given, though not 

 circumscribed; it is determined, not by a boundary 

 line without, but by a central point within; not by 

 what it strictly excludes, but by what it eminently 

 includes; by an example, not by a precept; in short, 

 instead of Definition we have a Type for our director. 



" A Type is an example of any class, for instance 

 a species of a genus, which is considered as eminently 

 possessing the character of the class. All the species 

 which have a greater affinity with this type-species 

 than with any others, form the genus, and are ranged 

 about it, deviating from it in various directions and 



