I S73-] Molecular Motion. 431 



term law in an improper sense. Law in physics is not an 

 agent or force, it is simply the process or mode of operation 

 — not the force, but the path along which the force acts. 



A prodigious number of physical phenomena are perceived 

 to follow as necessary consequences from Newton's grand 

 law, that bodies tend toward each other with a force vary- 

 ing inversely as the square of the distance and directly as 

 the mass of the bodies. But we should reach a higher 

 unity and obtain a deeper insight into nature did we know 

 not merely the empirical fact that bodies do so, but the 

 cause why they do so. It is this which incites in the 

 rational physicist the desire to find out the cause of gravity, 



But be all this as it may, whether it be Cause or Law, 

 that is the thing which we are really in search of, every 

 one will admit that the problem of deepest interest is, what 

 causes the molecules and particles of living nature to 

 arrange themselves into organic forms ? The problem is 

 not what moves the particles, but what determines or directs 

 the motion — or, in other words, what is the cause of the 

 determination of motion ? 



What, then, determines molecular motion in organic 

 nature ? What determines and directs the action of the 

 forces concerned in the production of specific forms in the 

 inorganic and organic world ? Is it a Force ? This leads 

 us to Mr. Croll's second proposition, viz. — The action of a force 

 cannot be determined by a force, nor can motion be determined by 

 motion. 



That the action of a force cannot be determined by the 

 action of a force is demonstrable thus. If the action of a 

 force is determined by an act, then this determining act 

 must itself have been determined by a preceding act ; and 

 this preceding act by another, and so on in like manner to 

 infinity. This is evident ; for if the act which determines 

 the action of the force exist at all, it must exist in time and 

 space, and must have a determinate existence in reference 

 to time and space, and if so, something must have given it 

 that determinate relation. If it be replied that it was a 

 prior act which determined this determining act, then that 

 prior act in order to give the determining act the proper 

 determination must itself have been already properly deter- 

 mined ; and the question again recurs, what gave this prior 

 act the proper determination ? If the determination was 

 given by an act still prior, that act must itself have been 

 properly determined ; and if so, then there must have been 

 another act preceding which gave it the proper determina- 

 tion, and so in the like manner to infinity. The reason of 



