998 Dynamic Theory. 



Now it has been said that nerves and cells, and the current of ner- 

 vous energy can be described "in terms of matter and motion," while 

 (the sensation) red cannot. At first sight this may appear so, especi- 

 ally if we fail to reflect that we are by no means acquainted with all 

 the "terms of motion." For a thousand generations men knew that 

 if a blacksmith should pound a piece of cold iron it would get hot. 

 They would have described the operation of pounding in "terms of 

 motion," but they never suspected that the heat imparted to the iron 

 could be described in terms of motion too. It did not look anything 

 at all like what they had been accustomed to regard as motion of mat- 

 ter. And in truth it has no resemblance to the waving of a flag, or the 

 falling of a stone, or the flight of an arrow; and the proof that it is 

 energ} r , or the motion of matter is circumstantial. We see energy con- 

 sumed in getting the iron hot and with proper contrivance we can get 

 energ}^ out of it as it parts with its heat. It is in just such a way that 

 we get at the conclusion that there is the progressive molecular agita- 

 tion of the nerve fiber which we call current, ending in a cell agitation 

 which we call red. We see energy consumed, can trace its movement 

 and perceive its manifestation as sensation red. I admit sensation red 

 does not seem to us at all like many other sorts of motion. It has 

 little resemblance for example to the stroke of a bell-clapper. But the 

 vibration of the bell following the stroke of the clapper does not much 

 resemble it either. This is followed by the vibration of the air which 

 does not seem like red, nor like the stroke of the clapper. And lastly 

 in this series is the sensation sound, which has no resemblance to stroke 

 of clapper, or to sensation red. But we feel sure that sensations sound 

 and red do belong to the same genus of phenomena. They are both 

 motion of the same sort of substance whatever it is. So the stroke of 

 the clapper and the current up the optic nerve are both motions of mat- 

 ter, but they strike us as being no more like each other than either is 

 like red or sound. We do no violence to any fact we know in relation 

 to them when we describe all four of these phenomena in the same 

 terms of motion. Thus they are imponderable and absolutely destitute 

 of density. Although inseparable from matter, they are not matter. 

 There is one positive attribute they all possess in common, and that is 

 quantity. (Matter also possesses an attribute we call quantity, but the 

 two can scarcely be said to be alike). Each one supervenes and subsists 

 upon the disappearance of an antecedent form of motion, and is one of 

 an infinite series in time, and part of definite quantity, which as a 

 whole is indestructible, and which cannot be increased or diminished. 

 There is this difference between sound and movement of the bell-clap- 

 per, that the former is part of our own personality while the latter is 

 not. We may get more than one sort of sensation from the movement 



