xxxi.] LIMITS OF SCIENTIFIC METHOD. 745 



believing in Creation at an assignable date in the past, or 

 else of supposing that some inexplicable change in the 

 working of natural laws then took place. Physical science 

 gives no countenance to the notion of infinite duration of 

 matter in one continuous course of existence. And if in 

 time past there has been a discontinuity of law, why may 

 there not be a similar event awaiting the world in the 

 future ? Infinite ingenuity could have implanted some 

 agency in matter so that it might never yet have made 

 its tremendous powers manifest. We have a very good 

 theory of the conservation of energy, but the foremost 

 physicists do not deny that there may possibly be forms of 

 energy, neither kinetic nor potential, and therefore of un- 

 known nature. 1 



We can imagine reasoning creatures dwelling in a world 

 where the atmosphere was a mixture of oxygen and in- 

 flammable gas like the fire-damp of coal-mines. If devoid 

 of fire, they might have lived through long ages unconscious 

 of the tremendous forces which a single spark would call 

 into play. In the twinkling of an eye new laws might come 

 into action, and the poor reasoning creatures, so confident 

 about their knowledge of the reign of law in their world, 

 would have no time to speculate upon the overthrow of all 

 their theories. Can we with our finite knowledge be sure 

 that such an overthrow of our theories is impossible ? 



The Ambiguoiis Expression, " Uniformity of Nature." 



I have asserted that serious misconception arises from 

 an erroneous interpretation of the expression Uniformity of 

 Nature. Every law of nature is the statement of a certain 

 uniformity observed to exist among phenomena, and since 

 the laws of nature are invariably obeyed, it seems to follow 

 that the course of nature itself is uniform, so that we can 

 safely judge of the future by the present. This inference 

 is supported by some of the results of physical astronomy. 

 Laplace proved that the planetary system is stable, so that 

 no perturbation which planet produces upon planet can 

 become so great as to cause disruption and permanent 

 alteration of the planetary orbits. A full comprehension 



i Maxwell's Theory of Heat, p. 92 



