CLASSIFICATION. 381 



Bentham indeed long ago stated P. We may always put 

 an arbitrary limit to the subdivisions of our classification 

 at any point convenient to our purpose. The crystallo- 

 grapher would not generally consider as different species 

 of crystalline form those which differ only in the degree of 

 development of the faces. The naturalist overlooks innu- 

 merable slight differences between plants or animals which 

 he refers to the same species. But in a strictly logical 

 point of view classification might be carried on so long as 

 there is a single point of difference, however minute, 

 between two objects, and we might thus go on until we 

 arrived at individual objects which are numerically distinct 

 in the logical sense attributed to that expression in the 

 chapter upon Number. We must either, then, call the 

 individual the infima species or allow that there is no 

 such species at all. 



The Tree of Porphyry. 



The bifurcate method of classification, arising as it does 

 from the primary laws of thought, is the very founda- 

 tion of all strict scientific method, and its application in 

 formal logic constitutes the method of Indirect Inference, 

 of which the nature and importance were shown in Chap- 

 ter VI. So slight, however, has been the attention paid 

 to this all important subject, that I shall in this case 

 break the rule which I have laid down for myself, not to 

 mingle the subject of logic as a science with the history 

 of logic. 



Both Plato and Aristotle were fully acquainted with 

 the value of bifurcate division which they occasionally 

 employed in an explicit manner. It is impossible, too, 



P < Outline of a New System of Logic/ 1827, p. 117. 



