SEGREGATION. 493 



society segregations of those units which have either a 

 natural likeness or a likeness generated by training. 



169. Can the general truth thus variously illustrated 

 be deduced from the persistence of force, in common with 

 foregoing ones? Probably the exposition at the beginning 

 of the chapter will have led most readers to conclude that it 

 can be so deduced. 



The abstract propositions involved are these: First, 

 that like units, subject to a uniform force capable of produc- 

 ing motion in them, will be moved to like degrees in the same 

 direction. Second, that like units if exposed to unlike forces 

 capable of producing motion in them, will be differently 

 moved moved either in different directions or to different 

 degrees in the same direction. Third, that unlike units if 

 acted on by a uniform force capable of producing motion in 

 them, will be differently moved moved either in different 

 directions or to different degrees in the same direction. 

 Fourth, that the incident forces themselves must be affected 

 in analogous ways : like forces falling on like units must be 

 similarly modified by the conflict; unlike forces falling on 

 like units must be dissimilarly modified; and like forces fall- 

 ing on unlike units must be dissimilarly modified. These 

 propositions admit of reduction to a still more abstract form. 

 They all of them amount to this: that in the actions and 

 reactions of force and matter, an unlikeness in either of 

 the factors necessitates an unlikeness in the effects; and that 

 in the absence of unlikeness in either of the factors the 

 effects must be alike. 



When thus generalized, the immediate dependence of 

 these propositions on the persistence of force, becomes obvi- 

 ous. Any two forces that are not alike, are forces which dif- 

 fer either in their amounts or directions or both ; and by what 

 mathematicians call the resolution of forces, it may be 

 proved that this difference is constituted by the presence in 

 the one of some force not present in the other. Similarly, 



