376 THE INDUCTIONS OF BIOLOGY. 



fore, to be groupings of objects which resemble one another in 

 external ot easily-perceived attributes, and attributes that are 

 not of complex characters. Those likenesses among things 

 which are due to their possession in common of simple obvious 

 properties, may or may not coexist with further likenesses 

 among them. When geometrical figures are classed as curvi- 

 linear and rectilinear, or when the rectilinear are divided 

 into trilateral, quadrilateral, &c.,the distinctions made connote 

 various other distinctions with which they are necessarily 

 bound up; but if liquids be classed according to their visible 

 characters — if water, alcohol, sulphuret of carbon, &c., be 

 grouped as colourless and transparent, we have things placed 

 together which are unlike in their essential natures. Thus, 

 where the objects classed have numerous attributes, the 

 probabilities are that the early classifications, based on simple 

 and manifest attributes, unite under the same head many 

 objects that have no resemblance in the majority of their 

 attributes. As the knowledge of objects increases, it becomes 

 possible to make groups of which the members have more 

 numerous properties in common; and to ascertain what 

 property, or combination of properties, is most characteristic 

 of each group. And the classification eventually arrived at 

 is of such kind that the objects in each group have more 

 attributes in common with one another than they have in 

 common with any excluded objects ; one in which the groups 

 of such groups are integrated on the same principle ; and one 

 in which the degrees of differentiation and integration are 

 proportioned to the degrees of intrinsic unlikeness and like- 

 ness. And this ultimate classification, while it serves to iden- 

 tify the things completely, serves also to express the greatest 

 amount of knowledge concerning the things — enables us to 

 predicate the greatest number of facts about each thing; and 

 by so doing implies the most precise correspondence between 

 our conceptions and the realities. 



§ 99. Biological classifications illustrate well these phases 



