. 219. THEORY OF THE SYSTEM. 323 



been really observed in octahedral Fluor-haloide, and ac- 

 knowledged as members of their respective series ; but we 

 know also, from . 218., that without in the least affecting 

 the relation to the idea of identity, they may arbitrarily be 

 exchanged with each other, and that we were even entitled to 

 produce or suppose the members of the two series I. and II. 

 if we had not had any occasion of observing them in nature. 

 The individual, whose remaining quality is expressed by N, 

 becomes thus = N. gg. H ; and this likewise is either an 

 object of our immediate observation, or it may be produ- 

 ced by connecting single observations.* Thus experience 

 confirms to its full extent, that several series of individuals 

 may be connected with each other in the manner described. 



An individual N. y. (X + n), can therefore be at the 

 same time a member of two different series, only under the 

 following conditions. Those of its properties which have not 

 been mentioned by name, and which are here expressed by 

 N, must agree with the properties analogous to them in the 

 two series ; and those which have been named (in the pre- 

 ceding case, forms, and colours), must be members of the 

 respective series, produced by the properties in the two 

 series of individuals. Under these circumstances, N. y. 

 (X + n) may be brought under the notion of identity 

 (. 218.) with the members of the first, but at the same 

 time also with the members of the second series. From 

 this we draw the inference, that all the members of om of 

 these series may be brought under the idea of identity^ with all 

 the members of the other. 



If we continue this process, and extend it upon all those 

 properties which form series by their gradations, we may in- 

 clude the assemblage of all those individuals, which, notwith- 

 standing their differences, may yet be brought under the idea 

 of identity. At the same time those individuals which do 

 not allow the process to be applied to them, are excluded 



* It is evident, that if it be found necessary thus to ob- 

 tain a determined object, the individuals of every well de- 

 termined natural-historical species may serve as examples. 



