382 INTRODUCTION TO PHILOSOPHY OF SCIENCE 



If the principle of indeterminacy is true, prediction is no 

 longer possible upon the grounds disclosed by the traditional 

 physics. But unpredictability is a limitation in our knowing 

 and cannot reasonably be employed as a basis for arguing 

 to the character of that which is known. 



Planck argues in somewhat this vein. The only indeter- 

 minism which is demonstrated by the Heisenberg principle 

 is a subjective indeterminism. He admits that the quantum 

 hypothesis has introduced a disturbance into the classical 

 theory of physics, and that "one cannot yet definitely say 

 what influence the subsequent development of the hypoth- 

 esis may have on the formulation of physical laws. Some 

 essential modification seems to be inevitable; but I firmly 

 believe, in company with most physicists, that the quantum 

 hypothesis will eventually find its exact expression in certain 

 equations which will be a more exact formulation of the 

 law of causality." l On the same question Einstein reports: 

 "I am entirely in agreement with our friend Planck in 

 regard to the stand which he has taken on this principle, 

 but you must remember what he has written. He admits 

 the impossibility of applying the causal principle to the 

 inner processes of atomic physics under the present state of 

 affairs; but he has set himself definitely against the thesis 

 that from this Unbrauchbarkeit or inapplicability we are to 

 conclude that the process of causation does not exist in 

 external reality." 2 "The indeterminism which belongs to 

 quantum physics is a subjective indeterminism." 3 



It is likely that the time is not yet ripe in physics for the 

 final solution to this controversy. More careful formulation 

 of the operational point of view is necessary before any 

 reconciliation is possible. In particular, the assumptions 

 involved in measurement must be brought to light. Empha- 

 sis has been placed earlier in the book on the necessity for 

 recognizing that an operational theory which admits meas- 

 urement techniques but denies measuring instruments is 

 insufficient. Measuring instruments are devised to measure 



1 Where Is Science Going?, p. 143. 2 Ibid., Epilogue, p. 210. 3 Ibid., p. 202. 



