216 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



what it may, it will always result in a force of special 

 intensity and special direction, acting upon the special 

 element of mass, and precisely the same sort of result, of 

 course, might follow from the action of some inorganic 

 combination. 



Under such a view there is room for all sorts of causes 

 of motion, whether they consist in the effect of systems of 

 " hidden masses," or in the effect of anything else : motion, 

 and motion alone, is studied by this kind of mechanics. 



That the special mechanical system of Hertz is kinetic 

 at bottom, that it knows only motion as the cause of motion, 

 and therefore knows only one kind of energy, viz., kinetic 

 energy, does not come into account here ; his principle of 

 movement as such would hold for any other theory of 

 dynamics equally well. 



Tlie Forms of Mechanical Causation 



But the problem of inorganic causation of motion 

 almost put aside by Hertz and " solved " in a rather abrupt 

 manner * now demands an answer. The two chief classes 

 of possible mechanics kinetics and dynamics at least 

 require to be considered. 2 



Kinetic mechanics knows only motion as the cause of 



1 By the assumption of stiff or rigid "connexions." This assumption fails 

 even to fulfil the requirements of the theory of elasticity. 



2 Kinetic mechanics may appear in two different forms, the one founded 

 upon the hypothesis of the continuity of matter, the other upon discontinuity. 

 Dynamical mechanics, of course, regards matter as discontinuous with regard 

 to its atoms, which are "centres of force," but its "lines of force" fill 

 space continuously whether they be regarded as mere abstractions or as 

 "states" of a continuous ether. Kinetic mechanics based upon continuity 

 cannot speak of "motion" in the ordinary sense of the word. "Motion" 

 becomes equal to " continuity and contiguity of change of elements of space." 



