CHAPTER VIL 
THE TWO BEST ILLUSTRATIONS. 
“ More particulars 
Must justify my knowledge.” 
—Cymbeline. Act ii., sc. 4. 
WHEN a particular department of nature is selected for 
the exposition of some general principle, the object may 
be to illustrate the action of what is believed to be a 
universally acknowledged law of nature, or else to test 
the correctness of a tentative theory. There can be no 
doubt whatever as to the advantage, so far as explanation 
is concerned, of a concrete illustration of an abstract 
principle. “ The philosopher,” says Dugald Stewart, 
“whose mind has been familiarised by education and by 
his own reflections to the correct use of more compre 
hensive terms, is enabled ... to arrive at general theorems ; 
which, when illustrated to the lower classes of men in 
their particular applications, seem to indicate a fertility 
of invention little short of supernatural.”* This principle 
is duly recognised by Mr. Romanes, when he says that 
“perhaps the proof of Natural Selection as an agency of 
the first importance in the transmutation of species may 
be best brought home to us by considering a few of its 
applications in detail. 1 ”f 
Now it is perfectly legitimate for those who approach 
the consideration of a particular group of phenomena, to 
* Elements of The Philosophy of the Human Mind. Part i., chapter iv. 
t Darwin and After Darwin, p. Ji6.