The Metaphysics of a Naturalist 
17 
dition, so looking at the brain as a mechanism for mental work> 
we find it set on a hair-trigger, and a breath on an eyelash is 
adequate stimulus to liberate vast stores of readjusting energy. 
All questions of the nature of sensation as well as of other 
mental activities hinge on the view taken as to the nature of con- 
sciousness. As consciousness is by its nature confessedly beyond 
the reach of analysis, we are forced by circumlocution to describe 
it in terms of its neurological concomitants. From many con- 
siderations, especially the structural coordinations and the 
unitary nature of consciousness, it seems most reasonable to 
conclude that the physiological basis of consciousness is the bal- 
ance or counterpoise of the cortical stimuli. 
From this point of view when the sensory stimulus is admitted 
to a cortical station there is at once a change of equilibrium — a 
setting of the neural excitement in the cells stimulated toward 
the rest of the cortical complex. This tide of nervous activity 
will obey laws of force, finding paths of least resistance, etc. 
The brain is so formed that it is possible for a great variation in 
the permeability to stimuli to exist at different times without any 
marked modification in the number or arrangement of the elements. 
It may be that the extent of the neurodendrites is the most 
important factor. It is known that the number and divisibility 
of these processes increases from youth to maturit}^ While they 
greatly increase the range of possible coordination (association), 
their presence may also serve to increase the total resistance and 
give rise to a sort of mental inertia. Most of the problems con- 
nected with sensation are connected with the content of sense and 
in reality belong to physiology and not psychology. Yet since 
the method used employs introspection in the study of this 
content, it may find a place in the psychological domain. The 
reason why one sense-content finds more ready entrance to the 
mechanism of consciousness in any given case may be found in 
the intensity of the neurosis, in the frequency with which its 
path has been before used (habit) or the state of equilibrium at 
the time existing in the cortex. If the neural tide is already 
setting away from a point of disturbance in the auditory center it 
will be somewhat more difficult to force a new wave from the 
visual center. The psychological study of sensation reduces to 
the study of the laws of association, and the great bulk of matter 
discussed under sensation is found to belong with the study of 
sense-content. 
