QUANTUM METAPHYSICS - E-thesis

used for measurement defines the conditions in which a phenomena occurs. The basis for
physical interpretation and theory are concrete changes in the measuring devices which can be
described in classical terms. These are things that must be assumed as starting points and it is not
necessary for theory to explain them. 705 The lack of a clear mental model concerning
measurement does not have to mean, as Mittelstaedt concluded, a deficiency concerning reality.
Neither does it mean a lack of completeness in the sense that quantum theory could not be
considered to be universal.
The understanding of measurement in different interpretations
As measurements are the foundation for any physical theory, it is no surprise that the question
concerning the proper interpretation of quantum theory also culminates in the measurement
problem. The conflict between Copenhagen and post-Copenhagen ways of approaching reality
and positioning human beings within it can be illustrated in their different treatments of the
measurement problem. In general terms, the Copenhagen interpretation emphasises the presence
of the observer in physical processes 706 , while the post-Copenhagen interpretations have
attempted to retain classical ideas concerning measurement; i.e. the ideals of detached observer
and objective description. It should, however, be kept clearly in mind that the Copenhagen
interpretation has dealt with measurement in two completely-different ways - even though both
of them emphasise the role of the observer.
In 1932, John von Neumann tried in his orthodox theory of measurement to find a traditional
objective solution to the problem by introducing the concept of the collapse of the wavefunction.
Simply stated, this postulate says that measurement causes an abrupt and irreversible
transformation in which a pure state turns into a mixture of states. Development of a quantum
mechanical system could, therefore, happen in two different ways and measurements should be
treated differently from all other interactions in nature. Von Neumann did not provide any clear
explanation for his projection postulate, but the concept has subsequently led to idealistic and
705 This point can also be expressed by saying that whereas classical physics tried to explain material objects with
atoms, Bohr tries to explain atomic phenomena using macroscopic objects which have permanent marks created and
observed in them.
706 In a way comparable to that of Bohr, Heisenberg writes "In quantum mechanics, the departure from the classical
ideal of objective descriptions has been radical... naturally it still makes no difference whether the observer is a man,
an animal or a piece of apparatus, but it is no longer possible to make predictions without a reference to the observer
or the means of observation. (To that extent, every physical process may be said to have objective and subjective
features.) Heisenberg, 1971, 88.
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