Ralph D, particle physics, and BS

Rahul Mahajan rahul at hagar.ph.utexas.edu
Fri Jun 23 04:44:39 MDT 1995

A few comments, Justin:

If by "grand unified theory," you mean what physicists usually mean (a
first step beyond the standard model), no such theories address the issue
of quantum indeterminacy. Even more generally, any current theories (e.g.,
string theories) unifying the four interactions have no bearing on the
issue. There have, of course, been theoretical developments in a different
direction, stating from at least the '50's, specifically addressed to
epistemological issues in QM. I'm not excessively familiar with this
literature, but it's certain that they haven't come close to a solution of
this issue. Actually, the many-worlds idea, which of course seems utterly
loony, makes a big step towards reinstating determinism; the collapse of
the wavefunction is a deterministic process -- every time it happens, you
create an exactly calculable ensemble of universes. If you now came up with
a deterministic model of what makes the wavefunction collapse, you would
have a deterministic view of the multiverse. Of course, it does seem like a
despicable evasion of the issue.

If anyone wants to bring the idea of chaos into the discussion of
determinism, it's strictly irrelevant. The whole field is devoted to
finding chaos as a feature of certain deterministic systems. Roughly
speaking, a system is chaotic near a point if trajectories in a
neighborhood of that point diverge exponentially with time. A nonchaotic
system may have linear or quadratic divergence. Computability and
determinism are distinct issues; of course, computability of the future
implies determinism but not vice versa. And, of course, as long as you're
talking about a finite computer (including anything that could exist in the
universe), there are nonchaotic systems whose behavior cannot be computed
accurately indefinitely into the future.

The situation of parts of social science is clearly closer to that of
evolutionary biology than evolutionary biology is to fundamental physics.
Nevertheless, EB has made very great progress and economics, etc., have
not. I'm talking here about results, not methods. One thing that seems to
strongly distinguish the natural from the social sciences is the level of
standards for scientific work. An economist can easily build a theory from
0 or 1 known example and avoid execration. Evolutionary biologists have put
together thousands of detailed case studies from which they can deduce
certain general principles. Neoliberal economics, on the other hand, has an
impressive body of "theory" which has never worked in any application. I
know I'm overstating the case; what do all of you economists say? Of
course, much of biology is on that fringe -- every idiotic study that some
idiot thinks shows a "gene for criminality" gets publicity and serious
attention. I think power issues are not sufficient to explain the complete
lack of ability to set up standards of scientific rigor in the social
sciences. After all, human biology is a very politically loaded topic, yet
there are some clear standards for research, even if they seem to be
honored more in the breach these days.


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