376 INDUCTION. 



cause of night ; since these phenomena have invariably 

 succeeded one another from the beginning of the world. 

 But it is necessary to our using the word cause, that we 

 should believe not only that the antecedent always has 

 been followed by the consequent, but that, as long as the 

 present constitution of things* endures, it always will be so. 

 And this would not be true of day and night. We do not 

 believe that night will be followed by day under all imagi- 

 nable circumstances, but only that it will be so provided the 

 sun rises above the horizon. If the sun ceased to rise, which, 

 for aught we know, may be perfectly compatible with the 

 general laws of matter, night would be, or might be, eternal. 

 On the other hand, if the sun is above the horizon, his light 

 not extinct, and no opaque body between us and him, we 

 believe firmly that unless a change takes place in the pro- 

 perties of matter, this combination of antecedents will be 

 followed by the consequent, day ; that if the combination of 

 antecedents could be indefinitely prolonged, it would be 

 always day ; and that if the same combination had always 

 existed, it would always have been day, quite independently 

 of night as a previous condition. Therefore is it that we do 

 not call night the cause, nor even a condition, of day. The 

 existence of the sun (or some such luminous body), and there 

 being no opaque medium in a straight linef between that 

 body and the part of the earth where we are situated, are the 

 sole conditions ; and the union of these, without the addition 

 of any superfluous circumstance, constitutes the cause. This 

 is what writers mean when they say that the notion of cause 



* I mean by this expression, the ultimate laws of nature (whatever they 

 may be) as distinguished from the derivative laws and from the collocations. 

 The diurnal revolution of the earth (for example) is not a part of the constitu- 

 tion of things, because nothing can be so called which might possibly be termi-" 

 nated or altered by natural causes. 



t I use the words " straight line" for brevity and simplicity. In reality 

 the line in question is not exactly straight, for, from the effect of refraction, 

 we actually see the sun for a short interval during which the opaque mass of 

 the earth is interposed in a direct line between the sun and our eyes ; thus 

 realizing, though but to a limited extent, the coveted desideratum of seeing 

 round a corner. 



