- causes are unveiled. 
JANUARY 4, 1901.] 
years ago, said: ‘It is not enough to be 
acquainted with the facts; scientific knowl- 
edge begins only when their laws and 
Our materials must 
be worked up by a logical process ; and the 
first step is to connect like with like and to 
elaborate a general conception embracing 
them all. Such a conception, as the name 
implies, takes a number of single facts to- 
gether, and stands as their representative 
in our mind. We call it a general concep- 
tion, or the conception of a genus, when it 
embraces a number of existing objects; we 
call it a law when it embraces a series of 
incidents or occurrences.” What is the 
first example by which Helmholtz illus- 
trated his meaning? It is one drawn not 
from experimental science, but from com- 
parative anatomy, namely, the correlations 
of structure shown by the Mammalia. 
What was Helmholtz’s estimate of the his- 
torical point of view in biology? Here are 
his own words, spoken ten years after the 
appearance of the ‘Origin of Species’: 
“The facts of paleontological and embry- 
ological evolution were enigmatical won- 
ders as long as each species was regarded 
as the result of an independent act of crea- 
tion, and cast a scarcely favorable light on 
the strange tentative method which was 
ascribed to the Creator. Darwin has raised 
all these isolated questions from the condi- 
tion of a heap of enigmatical wonders to a 
great consistent system of development, and 
established definite ideas in the place of 
such a fanciful hypothesis as, among the 
first, had occurred to Goethe, respecting 
the facts of the comparative anatomy and 
the morphology of plants.”’ 
But, the ‘rational morphologist’ may 
reply, these words were spoken thirty 
years ago, and conditions have profoundly 
changed since Helmholtz passed this too 
favorable judgment. Let us see. In his 
address on the ‘ Principle of Comparison in 
Physics,’ delivered before the German As- 
SCIENCE. 
21 
sociation of Naturalists and Physicians at 
Vienna in 1894, that brilliant and versatile 
mathematical physicist, Ernst Mach, said: 
‘Comparison, as the fundamental condition 
of communication, is the most powerful 
inner vital element of science.” What is 
his first illustration of this truth? Again, 
as in the case of Helmholtz, it is drawn 
from non-experimental comparative mor- 
phology—from comparative anatomy and 
comparative embryology. ‘If it is not 
customary,” he continues, ‘to speak of 
comparative physics in the same sense that 
we speak of comparative anatomy, the rea- 
son is that in a science of such great ex- 
perimental activity the attention is turned 
away too much from contemplative element. 
But, like all other sciences, physics lives 
and grows by comparison.” 
It is needless to multiply such statements. 
Every really rational naturalist must admit 
that there is but one sane position to adopt, 
namely, to weleome any and every method 
by which our knowledge of organic nature 
may be advanced and unified. No one, I 
trust, will understand me to advocate the 
indiscriminate accumulation of facts—for 
this is not method, but the absence of 
method. The essence of science is not the 
accumulation of knowledge, but its organiza- 
tion.- Observation and experiment give us 
our materials, but it is the comparison and 
correlation of those materials that first 
build them into the fabric of science. As I 
regard the matter, it is therefore a reversal 
of the true standpoint to regard biological 
classification, in the broadest sense of the 
term, as no more than a preparation for ex- 
periment. Let us, however, admit that our 
science is entering on a phase in which 
experimental methods seem destined, and 
rightly so, to take the leading rank, and 
that to them we may probably look for the 
greatest advances that are to be made in 
years to come. Let us, too, admit that our 
existing systems of classification, our views 
