201 
CHAP. IV. 
ON THEORIES IN GENERAL$ AND ON THE MODES AND 
CONSIDERATIONS BY WHICH THEY ARE TO BE VERI- 
FIED. 
(136.) Ir has been shown, in the preceding chap- 
ter, that there are three modes by which the objects 
of nature may be classified; and that one of these 
— that is, the natural system —is alone conducive to 
the advancement of natural history as a physical 
science. To this, therefore, we shall hereafter con- 
fine our attention; because the principles of this 
science must be discovered by a similar series of 
inductive generalisations to those used in every de- 
partment of natural philosophy, ‘through which one 
spirit reigns, and one method of enquiry applies.” 
 (137.) Let us suppose, then, that an entomo- 
logical student, with a well-filled cabinet of unar- 
ranged insects, having his mind well stored with 
those simple facts regarding their structure and 
economy which he is to look upon as solid data—let 
us suppose him to commence the arrangement of 
the objects before him, according to what he thinks 
their true affinities, and with a view of verifying or 
discovering their natural arrangement. He com- 
mences by placing, one after the other, those species 
which bear the greatest mutual resemblance ; and 
for a time he proceeds so satisfactorily, — he finds the 
several links of the chain, as it were, fit into each 
