LAW, CAUSE 383 



something, and they must be calibrated over against that 

 something. Hence the method of measuring a given entity 

 cannot be exhaustive of the meaning of the symbol for that 

 entity. By position is meant not merely the method of 

 reaching the particle, but the qualitative feature of the par- 

 ticle which has been reached by this route ; by force is meant 

 not merely the method of reading indicators on spring bal- 

 ances and scales, but that qualitative feature of nature 

 which is correlated in a constant way with springs and 

 movements of beams; by motion is meant not merely the 

 quotient of a meter rod reading and a clock reading, but 

 that qualitatively given correlation of space and time which 

 exhibits itself to observation. Whether this refined notion 

 of operation has any important implications for the con- 

 clusion which may be drawn from the principle of indeter- 

 minacy remains to be seen. The importance of the principle 

 lies in the fact that it has compelled the scientist to pay 

 attention to operations ; no longer can the method of knowing 

 an event be neglected in the characterization of that event. 

 But, on the other hand, the principle has had the unfortunate 

 consequence of leading the scientist to believe that opera- 

 tions are exhaustive of meaning, and hence that the charac- 

 terization of the event is simply what is involved in knowing 

 the event. Both of these facts are important. What must 

 be decided now, before any ultimate reconciliation of the 

 opposed points of view can be achieved, is the precise ex- 

 tent to which one's knowledge of events is determined by 

 operations upon events and the extent to which it is de- 

 termined by the events themselves. This is the problem of 

 the future. 



REFERENCES 



R. B. Lindsay and H. Margenau, Foundations of Physics (New 



York: Wiley, 1936), Chap. X. 

 Victor F. Lenzen, Physical Theory (New York: Wiley, 1931), 



Chap. XVI. 

 Norman Campbell, What Is Science? (London: Methuen, 1926), 



Chaps. Ill, IV, VII. 



