THE PRINCIPLES OF SCIENCE 201 



cant? I believe we can, and do. As science matures, so does our con- 

 ception of causality. At the inception of modern science action-by- 

 contact was the only causal mechanism fully acceptable; and the 

 "unthinkable" notion that celestial bodies can attract each other from 

 a distance, through "empty space," was as repugnant to Newton as 

 to most of his adversaries. But, as earlier suggested, ultimately we 

 learn to find acceptable explanations in models other than those that 

 involve directly only mechanical pushes and pulls. Today, in con- 

 frontation of the phenomena of microphysical indeterminacy, the 

 concept of causality undergoes not destruction but a still further en- 

 largement. 



For an observed microphysical eflFect we still seek, if not causes, 

 then reasons, e.g., involving "chance" and the law of large numbers. 

 May it be objected that, of its very nature, "chance" cannot furnish 

 a sufficient reason? Suppose I find that in a large number of throws 

 of a well-balanced die each face has turned up very nearly one-sixth 

 of the time. For this observation have I not an amply sufficient reason 

 when I recognize the absence of any cause that favors one face as 

 against another? I feel in this sufficient explanation of how to requite, 

 if not wholly to satisfy, the quest for sufficient reason broached by 

 the concept of causality. For to me it appears, as to Lande, that: 



. . . random events take place continually, as C. S. Peirce remarked 

 long before the quantum age. There are not sufficient causes for every 

 event. 



On the other hand, there is sufficient reason for the lack of sufficient 

 causes when one accepts Leibniz's principle of cause-effect continuity. 

 This principle leads first to the conclusion that the reaction "always 

 yes" or "always no" respectively should be bridged by intermediate 

 reactions "sometimes yes and sometimes no," that is, by cases of in- 

 determinacy in an individual test, dominated by statistical averages. 



The destruction of the cosmological principle of determinism does 

 not, of course, leave even the purely heuristic concept of causality 

 entirely unscathed. Thus Planck observes that: 



If it is assumed that statistical laws are the ultimate and most pro- 

 found in existence, then there is no reason in theoiy why, when deal- 

 ing with any particular statistical law, we should ask what are tlie 

 causes of the variations in the phenomena? Actually, however, the 

 most important advances in the study of atomic processes are due to 



