H. Kragh ("Dirac: a Scientific Biography", Cambridge U.P., 1990) reports
a 1927 discussion between Dirac, Heisenberg and Born, about what 
actually gives rise to the so called "collapse" (reduction of waves packet). 
Dirac said that it is 'Nature' that makes the choice (of measurement 
outcome). Born agreed.  Heisenberg however maintained that, behind 

the collapse, and the choice of which 'branch' the wavefunction would 

be followed, there was "the free-will of the human observer".


I don't think this does justice to Born's views.  
He was not a realist about the wave function 
nor about its collapse.  His position was that 
the classical world was logically prior and 
necessary for shared knowledge to exist.  
Without it there could be no measured 
values and no records.

Brent, maybe so, but Born wrote the following: 
"The question of whether the waves are something 
"real" or a function to describe and predict 
phenomena in a convenient way is a matter of 
taste. I personally like to regard a probability 
wave, even in 3N-dimensional space, as a real thing, 
certainly as more than a tool for mathematical 
calculations ... Quite generally, how could we 
rely on probability predictions if by this notion 
we do not refer to something real and objective?" 
(Max Born, Dover publ., 1964, "Natural Philosophy 
of Cause and Chance", p. 107) 


You received this message because you are subscribed to the Google Groups 
"Everything List" group.
To post to this group, send email to everything-list@googlegroups.com.
To unsubscribe from this group, send email to 
For more options, visit this group at 

Reply via email to