the Fundamental Problem of Nature. 9 



find that it is produced by no such cause. The mere motion of 

 the planet is indeed due to these forces ; but the path taken by 

 the moving planet cannot be referred to forces at all. The cir- 

 cular path of the planet is not the result of forces, but of the way 

 in which the forces are applied. The planet moves in virtue of 

 centrifugal and centripetal force ; but it moves in a circular path 

 because these two forces are so adjusted to each other that the 

 one tends continually to pull the planet in a straight line towards 

 a point called the centre of the orbit, while the other tends con- 

 tinually to make it move at right angles to that line. But it 

 may be replied that this particular adjustment of the two forces 

 can be referred to a force ; for, according to the nebular hypo- 

 thesis, the motion of the planets in their orbits results as a con- 

 sequence from the condensation by gravitation of the nebulous 

 matter out of which the system was formed. It is no doubt in 

 all probability true that the entire energy of planetary motion 

 was derived originally from gravitation. The vis viva or mere 

 motion of the planets is the result of gravitation ; but the paths 

 of the planets — the direction taken by them — cannot be referred 

 to gravitation. The motion of rotation induced in the nebulous 

 mass — the thing which originally determined not only the sepa- 

 rate existence of the planets but the form of their orbits — cannot 

 be referred to gravitation, but to the way or manner in which 

 gravitation acted on the condensing mass. In the condensation 

 of the nebulous mass, if the particles had moved directly towards 

 the centre of gravity of the mass, no motion of rotation would 

 have been induced, and consequently neither planets nor orbits 

 would have ever existed. The paths, therefore, of planets are 

 not due to the condensation of the mass by gravitation, but to 

 the way in which gravitation acted upon the mass. Had the 

 mass condensed without rotating, all that is now the vis viva or 

 energy of the planetary motion would have appeared as heat. 



Hence that which determined the existence of the planets as 

 separate bodies, which determined that so much of the energy 

 of gravitation should be converted into vis viva of planetary mo- 

 tion instead of into heat, and which determined that the planets 

 should not only move but move in circular or elliptical orbits, 

 was not gravitation, but that something (whatever it may have 

 been) which caused the nebulous mass to condense in such a 

 way as to produce a motion of rotation. Our solar system is 

 therefore the result not of force merely, but also of the determi- 

 nation of force. When the matter is properly analyzed, we find 

 that all that belongs to force is merely the vis viva or energy 

 that the system possesses. The plan of its existence, the ar- 

 rangements of its separate parts, and in fact everything else that 

 can be predicated of it but mere energy, are the result of that 



