216 SCIENTIFIC METHOD IN PHILOSOPHY 



other inferring from the same datum something which 

 will exist an hour hence. 



Often a causal law involves not one datum, but many, 

 which need not be all simultaneous with each other, 

 though their time-relations must be given. The general 

 scheme of a causal law will be as follows : 



"Whenever things occur in certain relations to each 

 other (among which their time-relations must be included), 

 then a thing having a fixed relation to these things will 

 occur at a date fixed relatively to their dates." 



The things given will not, in practice, be things that 

 only exist for an instant, for such things, if there are any, 

 can never be data. The things given will each occupy 

 some finite time. They may be not static things, but 

 processes, especially motions. We have considered in an 

 earlier lecture the sense in which a motion may be a 

 datum, and need not now recur to this topic. 



It is not essential to a causal law that the object 

 inferred should be later than some or all of the data. 

 It may equally well be earlier or at the same time. The 

 only thing essential is that the law should be such as to 

 enable us to infer the existence of an object which we can 

 more or less accurately describe in terms of the data. 



II. I come now to our second question, namely : What 

 is the nature of the evidence that causal laws have held 

 hitherto, at least in the observed portions of the past ? 

 This question must not be confused with the further 

 question : Does this evidence warrant us in assuming the 

 truth of causal laws in the future and in unobserved 

 portions of the past ? For the present, I am only asking 

 what are the grounds which lead to a belief in causal laws, 

 not whether these grounds are adequate to support the 

 belief in universal causation. 



The first step is the discovery of approximate unanalysed 



