994 Dynamic Theory. 



every problem in conic sections, is a production reflecting relations real 

 or possible, between material objects, and possible to be put together 

 only through the means of sensations, following sensory impressions. 

 It is needless to say that no sensory impression ever followed the im- 

 pact of energy, reflected from an immaterial substance; simply be- 

 cause, by its definition, any substance, which reflects energy, is a ma- 

 terial substance. If no conception can contain any elements of energy, 

 not reflected from material bodies, then all conceptions must be of ma- 

 terial bodies, and a conception of an immaterial substance is, therefore, 

 impossible. 



The description of an immaterial thing is made up of negative defi- 

 nitions, den} T ing to it every qualit} r possessed by ponderable matter as 

 extension, weight, visibility, &c. , and of positive definitions assigning 

 to it qualities, which belong to the motions of matter, such as force, 

 quantity, &c. , and especially those motions of the nervous system, 

 which we call love, hate, consciousness, &c. The definitions then really 

 make it, not a thing, but a motion of a thing. A thing does not come 

 and go, as consciousness does. "When a particular brain cell is ere- 

 thised, there is consciousness. When the excitement of the cell is over, 

 the consciousness is gone, while the cell is still there. The thing re- 

 mains, while its motion, a non-thing, has ceased to exist. But having 

 assumed, absolutely without proof so far discoverable, the existence of 

 an immaterial substance, what then is known about its properties? 

 "If an immaterial substance may exist, it may have any conceivable 

 properties, and sensation may be one of them. " Since assumptions 

 don't cost anything, you may as well assume a plent}' while you're as- 

 suming. But if after compelling yourself to believe you are thinking 

 of an unthinkable immaterial substance, }^ou have still got to assume 

 that it is endowed with sensation, I do not see what has been gained. 

 This assumption could have been made in the first place, in regard to 

 the sensorium if nothing better than assumption presented itself. 



The immaterial substance may have sensation for one of its proper- 

 ties, and then again it may not. I do not pretend to say that it is con- 

 ceivable how a mode of motion of brain elements is a sensation. I 

 only contend that the facts indicate quite positively that it is so, and 

 being so it is just as conceivable as most other things we are obliged to 

 accept, as gravitation, chemism, the construction of water, and of flame, 

 growth, &c. And it is just as conceivable as the notion that movements 

 of an immaterial substance could constitute mind. My principle ob- 

 jection to the immaterial conjecture is not so much that it is inconceiv- 

 able, as that it is utterly baseless and unsupported by a single fact in 

 any part of the universe accessible to us. Then why lias it been con- 

 sidered necessary to make this violent and unnatural assumption which 



