our 
946 The Relations of Mind and Matter. [October, 
received unconsciously, this is due to the activity of the attention 
in some other direction. But if the attention is disengaged, every 
sensation may produce consciousness, no matter how familiar a 
visitant it may be to the mind. 
The fact that when the mind is actively conscious in one direc- 
tion it may be unconscious of the operation of important move- 
ments previously set up within its organism, or of the reception 
of new sensations, seems to indicate that the volume of conscious- 
ness which may exist at any one time is limited. It may sink 
below this volume, even to complete disappearance during inac- 
tivity of the brain, but it cannot rise above it. And the variations 
in the distribution of this volume of consciousness are of the 
utmost interest and importance. Now it seems to diffuse itself, 
and a broad field of the mind is perceived, the central ideas in the 
field of vision being clear, while others crowd more faintly in, 
like dimly-seem objects which crowd in at the sides of the eye. 
Now it becomes concentrated, and only a few, or perhaps only a 
single idea is very vividly perceived if the powers of inward vision 
are acting with energy. And while, as a rule, sensations arrest 
the attention much more vividly than thoughts, this does not 
always hold. In some cases of mental diversion the most vivid 
sensations pass unperceived. 
This phenomenon of concentrated vision, as applied to the 
mind, has very important consequences. For the mind is utterly 
inactive except when energized by consciousness, and only that 
portion of it is active which is so energized. And as the activity 
of the mind governs the movements of the body, it follows that 
our voluntary actions, of whatever kind, are controlled, not by 
the mind as a whole, but by that portion of it which is active. 
This undeniable principle produces certain strange and important 
consequences. Ordinarily a certain number of our ideas are 
active, and particularly those deep-lying and firmly-based mental 
impressions and hereditary mental conditions which, acting to- 
gether, constitute what we call judgment, or common sense. But 
there are several normal and some abnormal states in which this 
condition is changed. 
One of these is in the case of strong emotion. As an earnest 
- desire fixes the eye intently upon some single object, and causes 
eye and mind alike to ignore what lies beyond this object, while 
the movements of the body are in response to the desire; so 
