Edgar Pearlstein
Lincoln, Nebraska
Only a theory is what creationists like to say about evolution;
and that seems to carry weight with some people. Such people don't
understand what that word means to a scientist.
As used in science, theory does not mean the same thing as
it does in everyday life. A theory is not a guess, hunch, hypothesis,
or speculation — it's much more full-blown, and the word is
by no means a pejorative term.
A theory is built upon one or more hypotheses, and upon evidence.
The word built is essential, for a theory contains reasoning
and logical connections based on the hypotheses and evidence. Thus
we have Newton's theory of gravity and the motion of planets, Einstein's
theory of relativity, the germ theory of disease, the cell theory
of organisms, plate tectonics (theory of the motion of land masses),
the valence theory of chemical compounds, and theories of evolution
in biology, geology, and astronomy. These theories are self-consistent
and consistent with one another.
Construction of good theories is a major goal of science.
Yes, a scientific theory can be wrong, as shown by experiment or
observation, since one of its hypotheses might be wrong or the reasoning
might be flawed or new data might come along that disagrees with
it; or its validity might be limited (as are some of those listed
above). So in science, a wrong theory gets discarded or modified.
This has happened, for example, with the caloric theory of heat in
physics and the phlogiston theory of combustion in chemistry.
In physics, which is my field, theories such as classical mechanics,
thermodynamics, and electromagnetism are thought to be on excellent
ground in both evidence and reasoning, but each of them is just
a theory. Other theories, such as in cosmology and elementary
particles, are still being developed, and do get changed as new evidence
and reasoning come in.
Supernatural creation is not a theory, but a hypothesis. Considered
in a scientific sense, it has a fatal flaw: it is sterile. If someone
asserts that there is a creator-god, one can ask “So what?” Nothing
follows from it; it leads nowhere. Some religions have additional
hypotheses, such as: only one creator-god, a great flood, the sun
standing still, a virgin birth, a trinity, the efficacy of prayer;
but no one of these is logically demanded, or even suggested, by
the others. They are just added on.
Anti-evolutionists sometimes say that evolution has not been “proven”.
In a strict sense, no theory is ever proven in any field,
with the possible exception of pure mathematics, since new data might
come along that requires a change, and there are always details that
haven't been tested. Sure, there are things not yet understood about
evolution, as in many other fields; but that is why scientists do
research! I have encountered the statement — meant as a put-down — that
scientists don't know everything. Well of course not, but we expect
to know tomorrow more than we know today.
Text ©2001 Edgar Pearlstein
Emeritus Professor of Physics, University of Nebraska
- Lincoln
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