43 2 Molecular Motion. [October, 



all this is perfectly obvious. When we account for the 

 determination of an act by assigning an act, we account for 

 it by means of a something which requires itself to be 

 accounted for in a similar manner. 



Hence, be the cause of the determination whatever it 

 may, it cannot possibly be an act or exertion of force. 



In a similar manner we can prove that motion cannot be 

 determined by motion. Motion will produce motion, but 

 motion cannot determine motion. A ball A in motion will 

 produce motion in a ball B, but the motion of the ball A will 

 not determine the motion of the ball B, either in regard to 

 direction or to the times of its happening. The particular 

 direction taken by the ball B is not due to the motion of A, 

 but to the particular direction in which A is moving at the 

 moment in which it produced motion in B ; so that the 

 direction taken by B must be referred not to the motion of 

 A, but to that something, whatever it may be, which causes 

 A to move in the particular direction in which it moves. 

 In other words, the determinate direction taken by B is not 

 due to the motion of A, but to the direction of the motion of 

 A. In like manner it can be proved that the direction 

 taken by A is not due to the motion of some other body 

 (say C), but to the direction of that moving body C. 



In a similar way we can prove that the particular time at 

 which B begins to move is not due to the motion of the 

 striking body A, but to the particular time at which the body 

 A strikes B. 



The vague and indefinite idea that the arrangement of 

 the molecules of matter into crystalline and organic forms 

 is due to the action of forces, appears to be implied in such 

 terms in common use as "structural forces," "formative 

 forces," " crystal-building force," &c. It is supposed that if 

 our mental .powers were enlarged or strengthened so that 

 we could perceive every thing connected with the forces 

 operating in nature, we should then be able to explain the 

 process by which the organic forms of nature are built up. 

 This, however, is evidently a mistake. Though our ac- 

 quaintance with the forces of nature were absolutely perfect, 

 the question as to how particles or molecules arrange them- 

 selves into organic forms would probably still remain as 

 deep a mystery as ever, unless we knew something more 

 than force. 



The mystery is not what are the forces which move the 

 particles, but what is it that guides and directs the action of 

 the forces so that they move each particle in the particular 

 manner and direction required. Force gives motion to the 



