36 INDUCTION. 



and must so continue while the causes subsist and are not 

 counteracted. 



3. In all cases of progressive effects, whether arising 



from the accumulation of unchanging or of changing elements, 



there is an uniformity of succession not merely between the 



cause and the effect, but between the first stages of the effect 



and its subsequent stages. That a body in vacuo falls sixteen 



feet in the first second, forty-eight in the second, and so on in 



the ratio of the odd numbers, is as much an uniform sequence 



as that when the supports are removed the body falls. The 



sequence of spring and summer is as regular and invariable as 



that of the approach of the sun and spring : but we do not 



consider spring to be the cause of summer ; it is evident that 



both are successive effects of the heat received from the sun, 



and that, considered merely in itself, spring might continue 



for ever, without having the slightest tendency to produce 



summer. As we have so often remarked, not the conditional, 



but the unconditional invariable antecedent is termed the 



cause. That which would not be followed by the effect unless 



something else had preceded, is not the cause, however 



invariable the sequence may in fact be. 



It is in this way that most of those uniformities of succes 

 sion are generated, which are not cases of causation. When a 

 phenomenon goes on increasing, or periodically increases and 

 diminishes, or goes through any continued and unceasing process 

 of variation reducible to an uniform rule or law of succession, 

 we do not on this account presume that any two successive 

 terms of the series are cause and effect We presume the con 

 trary ; we expect to find that the whole series originates either 

 from the continued action of fixed causes, or from causes which 

 go through a corresponding process of continuous change. A 

 tree grows from half an inch high to a hundred feet ; and some 

 trees will generally grow to that height, unless prevented by 

 some counteracting cause. But we do not call the seedling the 

 cause of the full-grown tree ; the invariable antecedent it cer 

 tainly is, and we know very imperfectly on what other antece 

 dents the sequence is contingent, but we are convinced that it 



