48 THE GRAMMAR OF SCIENCE 



psychical side of thought. It is merely intended to suggest 

 the manner in which we may consider thought to be 

 associated with its physical accompaniments. What the 

 actual relations between the psychical and physical aspects 

 of thought are, we do not know, and, as in all such cases, 

 it is best to directly confess our ignorance. It is no use, 

 indeed only dangerous, in the present state of our know- 

 ledge with regard to psychology and the physics of the 

 brain, to fill the void of ignorance by hypotheses which 

 can neither be proven nor refuted. Thus if we say that 

 thought and motion are the same thing seen from different 

 sides, we make no real progress in our analysis for we can 

 form no conception whatever as to what the nature in 

 itself of this thing may be. Indeed, if we go further and 

 compare thought and motion to the concave and convex 

 sides of the same surface, we may do positive harm rather 

 than good ; for convexity and concavity when accurately 

 defined by the mathematician are not different qualities, 

 but only degrees of the same quantity, curvature, passing 

 the one into the other through zero-curvature or flatness. 

 On the other hand, the distinction between the psychical 

 and physical aspects of brain activity seems to be essen- 

 tially one of quality, not of degree. It is better to 

 content ourselves in the present state of our knowledge 

 by remarking that in all probability sense-impressions 

 lead to certain physical (including under this term possible 

 chemical) activities of the brain, and that these activities 

 are recognised by each individual for himself only under 

 the form of thought. Each individual recognises his own 

 consciousness, perceives that the interval between sensa- 

 tion and exertion is occupied by a certain psychical 

 process. We recognise consciousness in our individual 

 selves, we assume it to exist in others. 



^ 5. — Other-Consciousness as an Eject 



The assumption just referred to is by no means of 

 the same nature as that which we make every moment 

 in the formation of what we have termed constructs from 



