224 SCIENTIFIC METHOD IN PHILOSOPHY 



these errors that Mach and others have urged a purely 

 " descriptive ' view of physics : physics, they say, does 

 not aim at telling us " why ' things happen, but only 

 " how ' they happen. And if the question " why ? ' 

 means anything more than the search for a general law 

 according to which a phenomenon occurs, then it is 

 certainly the case that this question cannot be answered 

 in physics and ought not to be asked. In this sense, the 

 descriptive view is indubitably in the right. But in 

 using causal laws to support inferences from the observed 

 to the unobserved, physics ceases to be purely descriptive, 

 and it is these laws which give the scientifically useful 

 part of the traditional notion of "cause." There is 

 therefore something to preserve in this notion, though it 

 is a very tiny part of what is commonly assumed in 

 orthodox metaphysics. 



In order to understand the difference between the kind 

 of cause which science uses and the kind which we 

 naturally imagine, it is necessary to shut out, by an effort, 

 everything that differentiates between past and future. 

 This is an extraordinarily difficult thing to do, because 

 our mental life is so intimately bound up with difference. 

 Not only do memory and hope make a difference in our 

 feelings as regards past and future, but almost our whole 

 vocabulary is filled with the idea of activity, of things 

 done now for the sake of their future effects. All 

 transitive verbs involve the notion of cause as activity, 

 and would have to be replaced by some cumbrous peri- 

 phrasis before this notion could be eliminated. 



Consider such a statement as, " Brutus killed Caesar." 

 On another occasion, Brutus and Caesar might engage 

 our attention, but for the present it is the killing that 

 we have to study. We may say that to kill a person is 

 to cause his death intentionally. This means that desire 



