Paul Arveson (
Mon, 3 Feb 97 10:58:21 EST

Bob DeHaan posted:

In your own field of chemistry, do you "observe things that have no 'causes'"
that can be explained only by quantum theory?

In biology we know that random events occur, notably random mutations (within
limits) of genetic material. Can these be traced back to quantum events, or
are they explicable by probability theory? I have never heard that
probability theory is related to quantum theory.

It seems to me that if quantum events are the only events to which quantum
theory applies, then the statement made by physicists that God plays dice
with the universe is a philosophical statement, not an empirical one. It
seems to me it is the former. My understanding of Aristotle's theory of
causation is very superficial at best. But I was surprised to see you
referring to his "formal" cause to suggest how quantum mechanics might affect
the real world. At least that is what I think you are doing. Are physicists
beginning to use Aristotle's formal cause in their thinking about causation?

It's an important set of questions, and I think a lot of people have similar
questions. Since you posted this to the whole group instead of only Terry
Gray, I will add my 2 cents worth.

I'm sure Terry will readily describe the traditional views of causality
from Aristotle's analysis to Newton and Einstein. But Heisenberg and
Erwin Schroedinger contributed the radical concept of indeterminacy which
Einstein dismissed with the (rather metaphorical in his context) comment
that God doesn't play dice.

No modern physicist seriously entertains the Newtonian or Laplacian concepts
of determinism, in which all motions can be determined in principle.
Newtonian mechanics is limited to the most simplified idealistic
examples, which makes it a good introduction to kinematics in Physics 101.

Remember Schroedinger's cat? The cat was placed in a box with a jar
of cyanide, that was connected to a timer and geiger counter. The timer
was set in such a way that there is a 50-50 chance of the cat dying
based on the decay of a radioactive atom. This was a thought experiment which,
among other things, demonstrated that there is no clear and definite
boundary between quantum causality and macroscopic causality. The
reality of quantum processes cannot be relegated to the microscopic world.
Furthermore, even without quantum physics, even with only Newtonian
assumptions, there is the possibility of chaotic and unpredictable-
in-principle processes, which were described by Poincare in his
version of celestial mechanics in the 19th century.

You will recall that recently, R.C. Sproul (whom I generally admire)
has been railing against 'chance' as the term is commonly used in
the popular scientific literature. For instance, Murray Gell-Mann
refers to human existence as due to 'accidents' of nature. To this
R.C. says, "Not a Chance!" Chance is nothing, and therefore
can be the cause of nothing.

But I don't think physicists mean to use the term chance this way.
In conversation often it is used as a 'shorthand' term to describe
something that if amplified would be like this: You start with
a pre-existing group of particles or atoms or molecules. They are in
thermal motion. They constantly shift their patterns in a very complex way.
The motion is unpredictable, but all kinds of arrangements are more
or less equally likely (probability). This complex, changing set
of patterns we refer to as 'random'. A particular event selected
from among these patterns may arise by 'chance'. Such random events
are real; they are not 'nothing'.

We as humans do not know -- and never can know -- the 'cause' of a
particular arrangement. You may say it is unknowable in principle
due to the nature of the quantum, or you may say it is too complex
for human experimenters to determine. Either way, it is unpredictable
from the human perspective, which is all the physicist has. And
among such processes are genes crossing over, and mutations....

An example of a clear exposition of quantum electrodynamics is given in
QED: the Strange Theory of Light and Matter, by Richard Feynman.
He takes a strongly 'instrumentalist' philosophical approach:
we don't know exactly how to describe quantum processes --
no one knows! The underlying processes -- involving not only
nondeterministic causes but even time reversal -- are admittedly
absurd. However, if we do the path integral mathematical calculations,
we arrive at predictions that agree with measured results of experiments
to 11 or 12 decimal places -- the most precise validation in
all of physics.

Such successes have led the physics community to agree with Feynman
and Heisenberg and Bohr, and to reject Einstein's alternative view.

There is a lot more to discuss about this issue from the theological
aspect. I don't have time to get into this, but it has been discussed
in this list previously.

Paul Arveson, Research Physicist
Code 724, Signatures Directorate, NSWC
9500 MacArthur Blvd., Bethesda, MD 20817-5700
(301) 227-3831 (W) (301) 227-4511 (FAX) (301) 816-9459 (H)