QUANTUM METAPHYSICS - E-thesis

subjectivistic interpretations which incorporate the suggestion that consciousness somehow
collapses the wavefunction.
Von Neumann carried out careful research into where the reduction (i.e. collapse) of the wave
function could be located. He divided the measurement chain into tiny parts and realised that the
line between the object and the measuring device was movable. In this way, his projection
postulate could be adapted to an object, a system consisting of an object and a measuring device,
or an even wider system which includes the sense organs and brain of the observer. Somewhat
against his will, Von Neumann was led to conclude that perhaps the best way to understand
collapse is if the line is drawn between consciousness and the brain. Utilizing this, Fritz London
and Edmond Bauer soon added the proposition that reduction of the wavefunction was not
perhaps a physical process, but one which required the consciousness of the observer. Collapse
of the wavefunction always occurred when the observer became conscious of some measurement
result. 707
Von Neumann’s measurement theory is usually taken as part of the Copenhagen interpretation,
even though Bohr rejected the subjective projection postulate and regarded the common attempt
to create a model of measurement in terms of quantum theory as wrong. Von Neumann’s
reduction postulate is assumed in several textbooks on quantum mechanics, even though it is
commonly believed that talk about collapse, reductions or jumps can, by the standards of
physics, only be metaphorical. 708 Even if there is no evidence that any kind of collapse really
takes place, avoiding the use of these metaphors when attempting to provide an objective model
concerning measurement has been difficult. A consequence of the projection postulate is that
measurement is considered to represent the state of the system being investigated immediately
after measurement takes place, while classical measurement is thought of as revealing properties
as they were prior to the measurement event. 709
Bohr did not accept Von Neumann’s method of approach, on the basis of which it was easy to
end up embracing Subjectivism or Idealism 710 . Bohr was silent on the question of the collapse of
the wavefunction. He did not accept the common requirement that quantum theory should
707 Herbert 1985, Murdoch 1987, 126-127.
708 No textbook on quantum measurement exists. The projection postulate is seldom covered in standard quantum
textbooks. These omissions show that a substantial account of the relationship between amplitudes and eigenvalues
is not required for a working understanding of quantum theories. Auyang 1995, 82.
709 Murdoch 1987, 122-126.
710 John Bell also noticed that Bohr rejected projection postulate and subjectivism. Bell 1997, 99.
265