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a body in itself non-sentient be sensation ? Who is it, 
tben, that feels ? Hovv does the sensation come about ? 
Where 
With these last words of Lange, the full difficulty of the 
problem opens upon us. Mere animal sentiency may perhaps 
exist without any degree of consciousness, as, for example, in 
the oyster. But the philosophy which would explain the 
Kosmos as the effect of the forces of matter must show those 
forces to be adequate causes of conscious sensation in man. 
Here, however, on the confession of men themselves strongly 
attached to atomic Materialism as a physical theory, we reach 
the brink of an impassable chasm. On the atomic theory, 
writes Lange {id., 23), ‘'^we explain to-day the laws of sound, 
of light, of heat, of chemical and physical changes in things, 
in the widest sense, and yet atomism is as little able to-day, 
as in the time of Democritus, to explain even the simplest 
sensation of sound, light, heat, taste, and so on. In all the 
advances of science, in all the modifications of the notion 
of atoms, this chasm has remained unnarrovved.'’^ Even 
when science shall have succeeded in constructing a com- 
plete theory of the functions of the brain, and in showing 
clearly the mechanical motions, with their origin and their 
result, which correspond to sensation, she will be (I again 
recur to the words of Lange) ^‘'for ever precluded from 
finding a bridge between what the simplest sound is, as 
the sensation of a subject, — mine, for instance, — and the pro- 
cesses of disintegration in the brain which science must assume 
in order to explain this particular sensation of sound as a fact 
in the objective world (Lange, -id., p. 23). To the same 
purpose Professor Tyndall, who, on this point, will not be a 
suspected authority, says, in his article entitled Yirchow and 
Evolution {Nineteenth Century, November, 1878), — ^‘'Here, 
however, the methods pursued in mechanical science come to 
an end; and, if asked to deduce from the physical interaction 
of the brain molecules the least of the phenomena of sensation 
or thought, we must acknowledge our helplessness. Between 
molecular mechanics and consciousness is interposed a fissure 
[the Professor is thinking of the Alpine glaciers] over 
which the ladder of physical reasoning is incompetent to 
carry us."’^ 
But, if no mechanical theory of the universe can account for 
mere sentiency, how complete must be the failure of every such 
system to take the last upward step from vital to mental, and 
to resolve the problems of human thought and feeling. The 
special case of those processes we call intellectual,^"’ says Lange, 
^^must be explained from the universal laws of all motion, or 
