SCIENCE AND MAN. 611 
and liberated the muscular power. Whence this impulse? 
From the center of the nervous system. But how did 
it originate there? This is the critical question, to 
which some will reply that it had its origin in the human 
soul. 
The aim and effort of science is to explain the unknown 
in terms of the known. Explanation, therefore, is condi- 
tioned by knowledge. You have probably heard the story 
of the German peasant, who, in early railway days, was 
taken to see the performance of a locomotive. He had 
never known carriages to be moved except by animal power. 
Every explanation outside of this conception lay beyond 
his experience, and could not be invoked. After long 
reflection therefore, and seeing no possible escape from the 
conclusion, he exclaimed confidently to his companion, 
" Es miissen doch Pferde dariu sein" There must be 
horses inside. Amusing as this locomotive theory may 
seem, it illustrates a deep-lying truth. 
With reference to our present question, some may be 
disposed to press upon me such considerations as these: 
Your motor nerves are so many speaking-tubes, through 
which messages are sent from the man to the world; and 
your sensor nerves are so many conduits through which the 
whispers of the world are sent back to the man. But you 
have not told us where is the man. Who or what is it 
that sends and receives those messages through the bodily 
organism? Do not the phenomena point to the existence 
of a self within the self, which acts through the body as 
through a skillfully constructed instrument? You picture 
the muscles as hearkening to the commands sent through 
the motor nerves, and you picture the sensor nerves as 
the vehicles of incoming intelligence; are you not bound 
to supplement this mechanism by the assumption of an 
entity which uses it? In other words, are you not forced 
by your own exposition into the hypothesis of a free human 
soul? 
This is fair reasoning now, and at a certain stage of the 
world's knowledge it might well have been deemed con- 
clusive. Adequate reflection, however, shows that instead 
of introducing light into our minds, this hypothesis con- 
sidered scientifically increases our darkness. You do not 
in this case explain the unknown in terms of the known, 
which, as stated above, is the method of science, but you 
