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THE PRINCIPLES OF BIOLOGY. 
THE PRINCIPLES OF BIOLOGY. 
BY HERBERT SPENCER. 
Exposition of Chapter XI. — On “Classification.” 
[Abstract.] 
BY PROF. W. HILLHOUSE, M.A., F.L.S. 
, Classification lias a two-fold purpose ; to render identi¬ 
fication more easy, and to organise knowledge. When a 
librarian arranges his books according to their authors’ 
names he renders the identification, i.e., the discovery of 
any particular one, easy, and he renders it easy likewise 
to insert in its proper position any work subsequently written. 
But this arrangement has one systematic weakness; the 
practical impossibility of finding a work of which you know 
everything excepting the smallest part—its author’s name. 
Or the books may be arranged according to subject, in which 
case grouping and sub-grouping to several degrees will, in a 
large library, have to be resorted to. Further, this involves 
some knowledge of the contents of the books, and, to be 
philosophical, a conception, to some degree definite, of not 
merely the present but the proximate, not to say ultimate, 
extent of knowledge. This latter method would of necessity 
come late in the history of books. 
Each of these methods is, but in varying degree, a 
classification by the attributes or properties of the books ; 
in the former case but one attribute, the author’s name, is 
used. Any other single attribute could equally be used, 
knowledge of the attribute being then alone required for 
identification ; the books can then be placed in definite order 
or series. In the other case several attributes may be in use, 
and variously in use, for each volume ; here, therefore, true 
linear arrangement becomes impossible, for there is no reason, 
other than empyrical, for giving priority to any group of 
books or to any book in a group; all that you can do is to 
constitute groups, of which you can indicate the relationship. 
The growth of such a method must be slow. 
Other things being equal, the relations amongst pheno¬ 
mena are recognisable in the order of their conspicuousness 
and simplicity. C (Eteris paribus, a child will more readily 
first recognise the male by a beard. Then all bearded males 
become “ papas.” With advancing perceptive powers differ¬ 
entiation comes into play, and with it a tendency to more 
