LAW OF CAUSATION. 399 



by the recently revived controversy on the old subject of 

 Plurality of Worlds, in which the contending parties have 

 been so conspicuously successful in overthrowing one another. 

 Here also we have experience only of a single case, that of the 

 world in which we live, but that this is inhabited we know 

 absolutely, and without possibility of doubt. Now if on this 

 evidence any one were to infer that every heavenly body 

 without exception, sun, planet, satellite, comet, fixed star or 

 nebula, is inhabited, and must be so from the inherent consti- 

 tution of things, his inference would exactly resemble that of 

 the writers who conclude that because volition is the efficient 

 cause of our own bodily motions, it must be the efficient cause 

 of everything else in the universe. It is true there are cases 

 in which, with acknowledged propriety, we generalize from a 

 single instance to a multitude of instances. But they must be 

 instances which resemble the one known instance, and not 

 such as have no circumstance in common with it except that 

 of being instances. I have, for example, no direct evidence 

 that any creature is alive except myself: yet I attribute, with 

 full assurance, life and sensation to other human beings and 

 animals. But I do not conclude that all other things are 

 alive merely because I am. I ascribe to certain other 

 creatures a life' like my own, because they manifest it by the 

 same sort of indications by which mine is manifested. I find 

 that their phenomena and mine conform to the same laws, 

 and it is for this reason that I believe both to arise from 

 a similar cause. Accordingly I do not extend the conclusion 

 beyond the grounds for it. Earth, fire, mountains, trees, 

 are remarkable agencies, but their phenomena do not conform 

 to the same laws as my actions do, and I therefore do not 

 believe earth or fire, mountains or trees, to possess animal 

 life. But the supporters of the Volition Theory ask us to 

 infer that volition causes everything, for no reason except that 

 it causes one particular thing ; although that one pheno- 

 menon, far from being a type of all natural phenomena, is 

 eminently peculiar ; its laws bearing scarcely any resemblance 

 to those of any other phenomenon, whether of inorganic or of 

 organic nature. 



