CAUSE AND EFFECT— PROBABILITY 117 



the phantasms with which metaphysicians fill the beyond 

 of sense-impression. Force will not, therefore, aid us in 

 our search for a scientific conception of cause. As we 

 have seen that there are two or even three ideas conveyed 

 by the one term law, so there are at least two ideas 

 associated with the word cause, and their confusion has 

 also led to as much " muddy speculation." Let us first 

 investigate the popular idea of cause and then see how 

 this is related to the scientific definition. A very slight 

 amount of observation has shown men that certain 

 sequences of change apparently arise from the voluntary 

 action, the will of a living agent. I take up a stone; no one 

 can predict with certainty what I shall do with it. What 

 follows my picking up the stone is to all appearances a 

 new sequence quite independent of any which preceded 

 it. I can let it fall again ; I can put it into my pocket, 

 or I may throw it into the air in any direction and with 

 any of a great variety of speeds. The result of my action 

 may be a long sequence of physical phenomena, to describe 

 which mechanically would require the solution of complex 

 problems in sound, heat, and elasticity. The sequence, 

 however, appears to start in an act of mine, in my will. 

 / appear to have called it into existence, and in ordinary 

 language I am spoken of as the caicse of the resulting 

 phenomena. In this sense of the word cause I appear to 

 differ qualitatively from any other stage in the sequence. 

 Had the hand of a stronger man compelled mine to throw 

 the stone, I should at once have sunk into a link in the 

 chain of phenomena ; he, not I, would have been tJie cause 

 of the resulting motion. 



It is certainly true that even in popular usage inter- 

 mediate stages ill the sequence will occasionally be spoken 

 of as causes. If the stone from my hand break a window, 

 the cause of the broken window might very likely be 

 spoken of as the moving stone. But although this usage, 

 as we shall see afterwards, is an approach to the scientific 

 usage of the word cause, it yet involves in the popular 

 estimation an idea of enforcement which is not in the 

 latter. That the stone moving with a certain speed must 



