PRINCIPLE OF VARIATION. 13k 
to all known animals? In proportion as we can de- 
monstrate the extent of the theory by which we propose 
to answer these questions, so do we approach the de- 
velopement of the natural system, and reduce the ele- 
ments of science to their most simple definitions. 
Finally, it results from these considerations that a theory | 
which embraces them all will exhibit a wnity of plan | 
which cannot possibly be the result of human ingenuity, 
and which will, consequently, be the nearest approach 
to that which must ever distinguish the natural system. 
Such are the obvious considerations by which we are to 
be guided in judging the merits of any classification 
which professes to be according to nature. In describing 
theoretically what should constitute the developement of 
the natural system, we have only alluded to those cir- 
cumstances which have already been partially developed, 
or which have been admitted as highly probable by 
others, who have, nevertheless, declared their inability 
to reconcile them with observed facts. 
(183.) Of natural systems, strictly speaking, there 
cannot, as we have already seen, be more than one ; 
but it is equally clear, that, if we confine this title to that 
one only which makes the nearest approach to nature, 
and which gives the fullest explanation of the pheno- 
mena she exhibits, we must term al/ other systems 
artificial, and thus confound, under one name, two de- 
scriptions of arrangements, which are grounded on to- 
tally different principles. In order, therefore, to mark 
their distinction with still greater precision, we shall 
consider all those systems to be artificial which are not 
grounded on any universal principles of arrangement ; — 
which exhibit the animal series without plan or harmo- 
nious connection,— and which disregard analogies and 
affinities. On the other hand, we shall consider those 
as natural systems which involve any one or more of 
these considerations, and which, looking beyond the in- 
dividual, attempt te ascertain its station in the scale of 
being, by pointing out the various relations which it 
respectively holds with other objects. From this view 
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