194 The American Naturalist. [Mareh, 
and, by its side, generating and directing its activities is its 
ever present companion the psychological life. Here then, we 
have a duplicate existence, extending over a finite period of 
years, incessantly changing from the time of its beginning, 
throughout the periods of growth, maturity and decay, and 
ultimately resolved, so far as human observation goes, into other 
existences of a lower order. 
Life, then is an existence. It is an existence characterized 
by incessant changes, and those changes are the manifestations 
of force. Hence, disregarding all ontological questions, the 
quantity of life may be measured like any other force, by the 
product of its intensity into the time of its duration. Let us 
‘now consider the factors which enter into and control the 
intensities of human life. Subjectively considered, life is ob- 
viously made up of a series of conscious experiences ; objectively 
considered, it is made of a succession of molecular and molar 
motions. To avoid too great complications we will consider it 
only subjectively, since the objective life has much in common 
with the motions of dead matter. 
Hobbes has well said “it is almost all one for a man to be 
sensible of one and the same thing, and not to be sensible at 
all of anything.” For instance the ticking of a clock contin- 
ued unintermittently through days, months, and years, forms — 
a rhythm in the conscious life which is equivalent to silence: 2 
Not until it ceases are we aroused to a consciousness of its 
former existence. The same is true of all familiar and oft ¢ 
repeated experiences. No matter how intense and vivid may — 
have been the first appeal of an experience, sooner OF later its 
reiterated occurrence establishes itself in the rounded and 
frictionless ruts of an indifferent consciousness. It might at 
first be inferred from this law, that for the conscious life to 
attain to its maximum intensity, it should experience the 
rarest stimuli; and those stimuli should be as intense as pos- 
sible. There is a limit however, beyond which nove ; 
to be impressive, and the over stimulated and flagging COD- 
sciousness relapses into apathy and indifference. But as & 
general rule we may be guided by Hobbes’ statement, and 
from its eonverse deduce the proposition, that the intensity of 
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