12 THE DOCTRINE OF DESCENT, 
These groups of facts, thus mutually referring to each 
other, must be, in some degree, examined by any one 
desirous of understanding them. In other words, we 
must first review this vast material, before we turn our 
attention to the magic spell which sifts and makes it 
comprehensible. The toil is great, but the reward is 
glorious! For, as regards the organic world, the craving 
inherent in the human mind for the knowledge of reasons 
—the need of causality, is satisfied singly and solely by 
the doctrine of Descent. As yet we do not regard it as 
complete; in many special cases it still owes us an 
answer ; but, on the whole, it does as much as any other 
ingenious theory has done; it interprets by a single prin- 
ciple those great phenomena which without its aid remain 
a mass of unintelligible miracles. In a word, it raises 
the knowledge of organic nature to a science. Even now 
much of mere professional knowledge is wont to style 
itself science. But as the doctrine of Descent includes 
all life, it cannot stop on approaching Man. Were we 
doubtful as to the origin of language, or even forced to 
admit total ignorance on this point, we could not, from 
the existence of language, deduce the inapplicability to 
man of the doctrine of Descent, without, as it seems to 
us, arbitrarily breaking the chain of ratiocination. 
We will now return to the preliminary question already 
indicated, as to the limits of the investigation of nature. 
It is the more important, as incompetent judges are 
wont to assert, that these limits are exceeded. The 
frivolity of the logic by which such accusations are ren- 
dered plausible to the multitude surpasses all licence. 
We open, for instance, Luthardt’s “ Apologetic Lectures 
on the Fundamental Truths of Christianity,” (“ Apolo- 
