THE PRINCIPLES OF SCIENCE 195 



ruled by "necessity," then causality expresses the aspiration to grasp 

 the nature of that necessity as distinct from the form of those laws. 

 Some modern physicists, like Weizsacker, seek to reduce causality 

 to nothing more than determinism. 



The criterion for the fact that one really knows the efficient cause, is 

 that one can predict correctly the event produced by it. Thus the 

 concept of cause has been so transformed, that the causal principle 

 in modern natural science has been identified precisely with the com- 

 plete predictability of natural phenomena. 



But though understanding may be manifested in the capacity to meet 

 this "criterion," it is not realized in, or constituted by, that capacity. 

 Through causality we seek, beyond knowledge of lohat-when- 

 tvhere, a grasp of the how of phenomena. 



The aspiration to grasp how was, we saw earlier, entirely respon- 

 sible for the naturalistic construction the Greeks put upon the prin- 

 ciple of determinism. And observe now in another instance at the 

 very beginning of the modern era that, once again, it is clearly the 

 conception of causality which controls application of the principle 

 of determinism. Thus Galileo laughs to scorn an alleged determinist 

 order simply on the ground that the causal connection it implies is 

 absurd: 



If Sarsi [Grassi] wants me to believe with Suidas that the Babylon- 

 ians cooked their eggs by whirling them in slings, I shall do so; but I 

 must say that the cause of this effect was very different from what he 

 suggests. To discover the true cause I reason as follows: "If we do not 

 achieve an effect which others formerly achieved, then it must be that 

 in our operations we lack something that produced their success. And 

 if there is just one single thing we lack, then that alone can be the 

 true cause. Now we do not lack eggs, nor slings, nor sturdy fellows 

 to whirl them; yet our eggs do not cook, but merely cool down faster 

 if they happen to be hot. And since nothing is lacking to us except 

 being Babylonians, then being Babylonians is the cause of the harden- 

 ing of eggs, and not friction of the air." 



Today, as noted at the end of Chapter VI, strictly analogous causal 

 considerations dominate our appraisals of statistical correlations of 

 data. Because we readily conceive a causal mechanism, we are pre- 

 disposed to judge significant a statistical correlation between cigaret 

 smoking and the incidence of lung cancer; and equally predisposed 



