30 SCIENCE (and common sense) 



... a close connection exists between the failure of our forms of per- 

 ception, which is founded on the impossibility of a strict separation of 

 phenomena and means of obsei-vation, and the general limits of man's 

 capacity to create concepts, which have their roots in our differentia- 

 tion between subject and object. 



This being conceded, Rosenfeld, not the least doctrinaire among 

 those who count themselves Bohr's disciples, still maintains that: 



... as far as quantum mechanics is concerned, I would say that it is 

 impossible to understand it without assuming that there is an external 

 world which is independent of what we think and which is the ulti- 

 mate origin of all our ideas. In that sense I absolutely reject the sug- 

 gestion of present-day positivists about the subjectivity of our state- 

 ments. 



Determinism. If I accept the possibility of prediction— whether by 

 common-sense relation or scientific law— I assume determinism. If 

 my past experience teaches me that state A is followed by state B, 

 then, observing a present occurrence of state A, I can predict the 

 future production of state B if and only if I assume the same condi- 

 tions are succeeded always, or at least statistically, by the same re- 

 sults. Prediction often proving possible, the assumption is in a meas- 

 ure justified. But even when prediction fails, rather than question the 

 assumption of determinism on which all hope of prediction depends, 

 I question instead the accuracy and completeness of my specification 

 of the conditions necessary to define state A. At once I seek (and 

 often I find ) a relevant variable earlier overlooked. 



Continuity. The creature endowed with instinct confronts the 

 apparently chaotic disorder of nature with patterns of fixed re- 

 sponses. That species of creature can then survive only if nature em- 

 bodies some general uniformity to which the fixed responses are, at 

 least statistically, appropriate. Instinct presupposes the continuity of 

 nature? However it may be with instinct, if I accept the possibility 

 of prediction I presuppose, over and above the principle of deter- 

 minism, a principle of continuity. Belief that state B will follow re- 

 liably on the attainment of state A means nothing if not coupled with 

 confidence that state A (or a good approximation to it) ivill recur. 

 We must then assume the "external world" continuous in time, in 

 location, and in species. We assume that things behave here and 



