A HISTORY OF SCIENCE 



finally, is that only those particles continue to move in 

 this region of space which have acquired by their fall 

 a velocity, and through the resistance of the other par- 

 ticles a direction, by which they can continue to main- 

 tain a free circular movement. . . . 



" The view of the formation of the planets in this sys- 

 tem has the advantage over every other possible theory 

 in holding that the origin of the movements, and the 

 position of the orbits in arising at that same point of 

 time nay, more, in showing that even the deviations 

 from the greatest possible exactness in their determina- 

 tions, as well as the accordances themselves, become 

 clear at a glance. The planets are formed out of par- 

 ticles which, at the distance at which they move, have 

 exact movements in circular orbits ; and therefore the 

 masses composed out of them will continue the same 

 movements and at the same rate and in the same direc- 

 tion:' 2 



It must be admitted that this explanation leaves a 

 good deal to be desired. It is the explanation of a 

 metaphysician rather than that of an experimental 

 scientist. Such phrases as " matter immediately be- 

 gins to strive to fashion itself," for example, have no 

 place in the reasoning of inductive science. Never- 

 theless, the hypothesis of Kant is a remarkable con- 

 ception; it attempts to explain along rational lines 

 something which hitherto had for the most part been 

 considered altogether inexplicable. 



But there are various questions that at once suggest 

 themselves which the Kantian theory leaves unan- 

 swered. How happens it, for example, that the cosmic 



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