8 De Vi Physic* 



abstract calculation, and all spheres legiti- 

 mately subordinate to it, in which things can 

 be treated in a purely quantitative way*. 

 But in the domain of Nature and Reality, 

 there are limits to the power and efficacy of 

 this principle of continuous increment. Its 

 omnipotence tends to disappear, in propor- 

 tion to the degree in which things cease to 

 be able to be considered as purely quantita- 

 tive magnitudes, and we enter the field of 

 qualitative and other real distinctions in 

 the economy of Nature. In the organic 

 world, where quantity is not everything, this 

 principle has explanatory value only within 

 very definite limits, and we require to be 

 very careful in attending to those limits, 



a e.g. Newton proved that a particle outside a hollow 

 sphere is attracted by it as if the spherical material were 

 collected at its centre : the same is true of a solid sphere, 

 because it may be legitimately considered, in a mechanical 

 point of view, as consisting of an infinite number of hollow 

 spheres one within the other. 



