DISCORDANCE OF ARTIFICIAL SYSTEMS. 155 
classification of the Mammalia, namely, Linneus, 
Cuvier, Illiger, and Hamilton Smith. Each of these 
studied from the same models,—models which are 
now the same as when they were first created; and 
each and all agree in the results of their respective 
examinations; that is, in the facts belonging to the 
structure of these animals. So far, therefore, we 
need not question their authority. But when they 
began to reason upon these facts, each drew separate 
inferences, and consequently produced different 
systems or methods of classification. These systems, 
however, make no reference to other parts of creation. 
They treat of the class before them, as if it was the 
only one in nature, and as if the principles by 
which it was to be arranged had no connection with 
those which governed other classes. We find, in 
short, no allusion to mutual resemblances out of this 
division of animals; so that an ordinary reader would 
suppose that nature had one system for quadrupeds, 
another for birds, a third for fish, and a fourth for 
insects. Did he turn to the best classifications of 
each of these orders now in use, he would be still 
further confirmed in this opinion, by seeing that 
they were all treated of in the same isolated and dis- 
connected manner. The ornithological systems of 
the greatest naturalists in this department differ 
from each other fully as much as those relating to 
quadrupeds, and are calculated to produce the same 
impressions. Seeing, therefore, that inferences may 
be innumerably various and discordant; by what 
rule, as the science now stands, are we to be guided 
in choosing truth? It is evident, that if there be 
but one system in nature, there can be but one 
