NoveMBER 5, 1896] 
NATURE 
4) 
re) 
life. The materialistic view-of life—the theory which 
would explain all organic and inorganic nature by force 
and matter—has disappeared owing to a wider and 
more philosophic view of mechanism, and not to the 
logic of vitalists. It is the physicists, and not the bi- 
ologists, who have broken down the barrier between the | 
exact and descriptive sciences, and among whom a truer 
view of mechanism has arisen. The biologists have been 
only too ready to offer “ explanations” of various organic 
processes by appeal to molecules, centres of force and 
energies. While they have been attempting a mechanical 
basis for descriptive science, the physicists have learnt 
that mechanics, after all, is but a descriptive science it- 
self. ‘The object of mechanics is to descriée in the 
simplest possible fashion the motions which occur in 
nature.” Such was Kirchhoff’s definition, and the ac- 
ceptance of that definition is really the revolution which 
has been going on in natural science. It is a revolution 
which cuts at the idea of force as a cause, but sees in it 
only a measure of change ; it is a revolution which thrusts 
upon us the agnostic position of watching and describing; 
and which drops explanation out of the scientific glos- 
sary or defines its old sense entirely away. It is a 
revolution which again renders for us the motion of a 
planet every whit as mysterious as the oscillations of 
protoplasm. We can explain neither, although long 
study and observation have enabled us to describe one 
motion in much simpler terms than the other. 
Mechanism as the description in the simplest possible 
terms, not the explanation, of natural motions is a revo- 
lutionary definition which at once reduces all physics, 
chemistry and biology to the same simple footing. In 
all three sciences it is the sequence of changes in space 
and time that we endeavour to describe in the simplest 
language. In doing this, we are inevitably thrown back 
on geometry and kinematics. The conceptions of these 
sciences are not identical with real experience ; they are 
based on ideal forms and ideal ratios drawn as limits from 
our experience of phenomena. But it is in terms of these 
only that we succeed in describing change, and this 
geometrical and kinematic description of change, and of 
repeated sequences of change is what we are to under- 
stand by mechanism in its broadest sense. It is this 
mechanism, which embraces such inventions of the in- 
tellect as particles, molecules, atoms and ethers, and | 
describes kinematically, or in terms of the motions it 
attributes to them, physical phenomena. Organic pheno- 
mena may require to be described by other conceptual 
elements having other modes of motion attributed to 
them than those which have hitherto been adopted in 
physical descriptions. But if organic phenomena are to 
be described scientifically, it must be by a series of sym- 
‘bolic forms moving in time and space. In this sense 
biology must ultimately become a mechanical science, 
‘This does not mean that life can be “explained” by 
mechanism—on the contrary, mechanism explains 
nothing, not even physical nature—but that the bulk of 
natural science is a description of change, of motion in 
time and space, and that the invention of comprehensive | 
and brief formule of motion is the function of mechanics. 
In this sense it seems impossible to contrast mechanism 
_and “vital force,” or to maintain any rigid line of demar- 
ation between the physical and descriptive sciences. 
NO. 1410, VOL. 55] 
From this standpoint, which we believe to be the firm 
ground, soon to be left behind by the sea of current 
erkenntnistheoretische controversies, how purely idle does 
Prof. Volkmann’s disquisition on natural laws, rules, 
hypotheses, and axioms appear! Thus Newton's law of 
gravitation, the principle of energy, Galilei’s law of 
inertia, he tells us, are Maturgesefze; Keplers laws of 
planetary motion are merely Aege/7, and the undulatory 
theory of light an Aypfothese! Yet Prof. Volkmann's 
definitions are worth noticing, because they show us so 
| very clearly the present transitional state of scientific 
thought. 
“Das Naturgesetz bildet den kiirzesten und zugleich 
reichhaltigsten Ausdruck fiir das, was  thatsachlich 
geschieht und zwar was ausnahmslos geschieht, was 
geschehen muss” (p. 58). 
It is the s¢zliche Wahrnehmung which changes the 
fiypothese to the Naturgese¢z. But we must ask, what 
physicist ever caught a particle, or had a sznmliche 
Wahrnehmung of how two particles. if caught, would 
attract each other? How is Newton’s particle more real 
than the atom of the chemist? Even Dr. Volkmann admits 
that the conception of the atom as something dz/d/ich 
symbolisch, is to-day winning ground everywhere. How 
can we have sinnliche Wahrnehmung of the law of inertia ? 
Does it not require the most ideal conceptions of relative 
motion and of “fixed axes” to at all realise its meaning ; 
and is it then more than a definition of acceleration? We 
cannot find this law so ecnleuchtend and so unmittelbar as 
Dr. Volkmann believes, nor consider that its essence 
can be scientifically illustrated by the motion of a loco- 
motive over smooth rails, when the steam is cut off. 
Indeed our author skates somewhat lightly over the 
abysmal gulf of the relativity of all motion. He has 
given up force as a reality, but the influence of relativity 
on all forms of kinetic energy does not appear to have 
struck him, and, like many another physicist, he would 
probably suppose we had some sinmliche Wahrnehmung 
of the absolute in a quantum of energy. The undulatory 
theory of light was purely hypothesis so long as it was 
iibersinnliche Anschauung und Vorstellung ; but now 
that the young German physicist Wiener has photo- 
| graphed light waves, we are told, that it has ceased to be 
an hypothesis, it has become ez7e vollendete Thatsache /— 
a law of nature. In not one of such natural laws, how- 
ever, is there anything of the szwss of Prof. Volkmann’s 
definition. They are purely dildlich symbolisch descrip- 
tions of motion, more or less simple, more or less complete 
and satisfactory. 
The reader will notice at once how far many students of 
science are yet from using the language and appreciating 
the ideas involved in Kirchhoff’s definition of mechanism. 
Mechanism, whether it be that of the particle, the atom, 
| the ether, or the cell, is a description of motion in the 
simplest terms the mind can invent, and this description 
is always in terms of those d7/dlich symbolische elements, 
| which we construct from such ideal sciences as geometry 
and kinematics. We may attach constants to these ele- 
ments to be determined by experience, and to be termed 
| charges, masses, &c., and, perhaps, in the distant future, 
when the science of vitalistics is complete, vital units ; 
| but the elements none the less remain d//dlich symbolisch. 
| They are mental constructs, by which the scientific mind 
