**Orthodox Interpretation**: Eugene Wigner, in a paper entitled *The
Problem of Measurement* (Wigner 1963), used the term "orthodox
interpretation" to identify the interpretation spelled out in
mathematical detail by John von Neumann in his book

*Mathematische Grundlagen der Quantnmechanik* (von Neumann 1932). Von
Neumann, in the chapter on the measuring process, shows how to expand
the quantum mechanical description of a system to include the physical
variables of the measuring device, or, more generally, the physical
variables of any system that interacts with an original system of
interest. He then gives a detailed analysis of the process of
measurement.

Von Neumann calls the unitary evolution of the quantum state (or wave
function) generated by the Schroedinger equation by the name "process
2". The process-2 quantum mechanical evolution is a mathematical
generalization of the deterministic evolution of a dynamically closed
system in classical physical theory. The quantum mechanical process 2,
like its classical counterpart, is deterministic: given the quantum
state at any time, the state into which will evolve at any later time
via process 2 is completely fixed.

Von Neumann considers an (idealized) situation involving a sequence of
physically described measuring devices each performing a good
measurement on the outcome variables of the preceding device, leading
eventually to the retina, then to the optical nerves, and finally to the
higher brain centers directly associated with the consciousness of the
observer. There is no apparent reason for the process 2 to fail at any
point, provided the full environment (essentially the entire physically
described universe) is included in the physical system. But in general
the process 2 evolution will lead to a state in which the higher brain
centers directly associated with consciousness will have non-negligible
components corresponding to different incompatible experiences, such as
seeing the pointer of a measuring device simultaneously at several
distinct positions.

Von Neumann notes that "It is entirely correct that the measurement or
the related process of subjective perception is a new entity relative to
the physical environment and is not reducible to the latter. Indeed, it
leads into the intellectual inner life of the individual, which is
extra-observational by its very nature (since it must be taken for
granted by any conceivable observation or experiment)."

To tie the quantum mathematics usefully to human experience von Neumann
invokes another process, which he called "process 1". Process 1
partitions the state into a particular collection of components each
corresponding to a distinct possible experience, but only one of which
will survive the "collapse of the wave function" or the "reduction of
the wave packet" associated with process of measurement or observation.

Wigner proves that process 1 can never be a consequence of process 2
alone: some other process, not the quantum analog of the deterministic
classical law of evolution, must come in. As in the classical case, one
must of course respect the condition that the quantum system be
dynamically closed. This means that if any macroscopic element is
included in the quantum mechanically described system then one must
effectively include the whole universe, due to the non-negligible
effects of the environment upon a macroscopic system.

Von Neumann notes that, in line with the precepts of the Copenhagen
interpretation, "we must always divide the world into two parts, the one
being the observed system, the other the observer", and that "quantum
mechanics describes the events which occur in the observed portion of
the world, so long as they do not interact with the observing portion,
with the aid of process 2, but as soon as such an interaction occurs,
i.e., a measurement, it requires an application of process 1."

The von Neumann/Wigner approach is, in this regard, not identical to the
Copenhagen interpretation specified by Bohr and Heisenberg, who, in
keeping with their pragmatic

epistemological stance, resist treating the entire physical universe as
a quantum system obeying the linear deterministic unitary law. Bohr ties
this limitation in the applicability of the normal quantum rules to the
fact that any attempt to obtain sufficient knowledge about any living
organism, in order to enable us to make useful predictions, would
probably kill the organism. Hence "the strict application of those
concepts adapted to our description of inanimate nature might stand in a
relationship of exclusion to the consideration of the laws of the
phenomena of life". (Bohr 1961, p. 22-23) This argument is effectively a
cautious suggestion that the breakdown of process 2 might be associated
with biological systems: i.e., with life. But von Neumann says "there
arises the frequent necessity of localizing some of these processes at
points which lie within the portion of space occupied by our own bodies.
But this does not alter the fact of their belonging to the 'world about
us', the objective environment referred to above."

Wigner's suggestion for dealing with this gross mismatch between the
process-2 generated activities of our brains and the contents of our
streams of conscious experiences, evidently stems from a desire to have
a rationally coherent *ontological* understanding of nature herself; an
understanding of the reality that actually exists. Noting that process 1
is associated with the occurrence of *observable* events, and hence the
implied need for an observer, Wigner suggest that the breakdown of
process 2 is due to the interaction of the physically described aspects
of nature with the consciousness of a conscious being (Wigner 1961) \[
Wigner's Friend\] This physically efficacious consciousness stands
outside the physically described aspects of nature controlled by process
2. Von Neumann calls it the observer's "abstract ego".

Conscious experiences are certainly real, and real things normally have
real effects. The most straightforward conclusion would seem to be that
process 1 specifies features of the interaction between the brain
activities that are directly associated with conscious experiences and
the conscious experiences with which those activities are associated.

This solution is in line with Descartes' idea of two "substances", that
can interact in our brains, provided "substance" means merely a carrier
of "essences" The essence of the inhabitants of *res cogitans* is "felt
experience". They are thoughts, ideas, and feelings: the realities that
hang together to form our streams of conscious experiences. But the
essence of the inhabitants of *res extensa* is not at all that of the
sort of persisting stuff that classical physicists imagined the physical
world to be made of.

They are indeed represented in terms of mathematically described
properties assigned to space-time points, but their essential nature is
that of "potentialities for the psycho-physical events to occur".. These
events occur at the interface between the psychologically and physically
described aspects of nature, and the laws governing their interaction
are given by von Neumann. The causal connections between "potentialities
for psychologically described events to occur" and such events
themselves are easier to

comprehend and describe than causal connections between the
corresponding features of classical physics. For, both sides of the
duality are conceptually more like "ideas" than like "rocks"..

**References**

Bohr, N. (1961): Atomic Theory and the Description of Nature,Cambridge
UK: Cambridge University Press.

Bohr, N. (1958): Atomic Physics and Human Knowledge, New York: Wiley.

Von Neumann, J, (1932): *Mathematische Grundlagen der Quantnmechanik,*
Springer, Berlin. (Translated as *Mathematical Foundations of* *Quantum
Mechanics,*

Princeton University Press, 1955)

Wigner, E. (1961): "Remarks on the Mind-Body Problem", in *The Scientist
Speculates*, I. J. Good, ed. pp. 284-302, London:Heinemann; Basic Books,
New York (1962).

Wigner, E. (1963): The Problem of Measurement. *American Journal of
Physics* 31, 6-15.