PART II. 

 THEORY OF THE SYSTEM. 



. 214. IDENTITY. 



Natural productions, which do not differ from 

 each other in any of their natural-historical proper- 

 ties, are identical (. 14.). 



This proposition is self-evident ; and it is the foundation 

 of the whole Theory of the System in Natural History. 



By considering in this science two bodies as identical, it 

 is meant that every one of them may be substituted in the 

 place of the other in every natural-historical respect ; so 

 that if the one belongs to a certain class, to a certain order, 

 genus, or species, the other likewise must necessarily belong 

 to the same class, to the same order, genus, and species. 



In considering the identity of two bodies, we must ab- 

 stract all accidental differences (. 25.). Such are, besides 

 the size of crystals, also the disproportionate enlargement 

 of some of their faces (. 159.), their junction with other 

 individuals, their being implanted or imbedded, &c. Indi- 

 viduals, which differ only in properties of this kind, must 

 be taken for identical ones, as well as those which agree 

 also in respect to these accidental circumstances. 



. 215. DIFFERENCE. 



Individuals, which do not agree in all their na- 

 tural-historical properties, are not identical. 



This proposition is an immediate consequence of the 

 preceding one. 



If two individuals agree in every one of their properties, 

 except in their crystalline form, or in colour, or iu hardness, 



