In
the New York Times a few days ago there was an article by Carl Zimmer
in the Science section. The article was entitled In Science, It's
Never “Just a Theory.” Zimmer asserts the following:
Theories
are neither hunches nor guesses. They are the crown jewels of
science.
Later
Zimmer makes this assertion:
A
theory, likewise, represents a territory of science. Instead of
rivers, hills, and towns, the pieces of the territory are facts.
So
generally speaking, scientific theories are made up of facts, and no
guesses? Hogwash. Rubbish. Zimmer is apparently a science theory
fanboy who we can expect to receive a scientific theory with the same
reverent enthusiasm that a trekkie might receive the next installment
of the Star
Trek
franchise. (The Merriam-Webster online dictionary defines a fanboy
as “a boy or man who is an extremely or
overly enthusiastic fan of someone or something.”) Let's
look at some things that conflict with this naive attitude toward
scientific theories.
Consider
some of the weird scientific theories that are floating about these
days. There is the Everett “many worlds” theory of parallel
universes, which imagines that the universe is constantly splitting
up into different copies of itself, and that there are a zillion
copies of you in different alternate universes, where everything
imaginable occurs. Then there's the Integrated Information Theory
which tries to explain consciousness in a way that implies that your
thermostat and cell phone are partially conscious. Then there's the
so-called “landscape” version of string theory, which
unnecessarily imagines something like ten to the five hundredth power
universes, each of which is a different permutation of string theory
(a speculative branch of physics that is entirely unproven). Then
there's Smolin's theory of cosmological natural selection, which
gives us the groundless speculation that certain type of stars spit
out new universes when they die. Then there's the panspermia theory
that life began on Earth because aliens planted it here. Then there
is Freud's theory that you have deep-rooted conflicts caused by your
subconscious sexual attraction to your mother. Then there are
neurological theories that your self is just an illusion.
Zimmer
would have us believe that scientific theories are in general “crown
jewels,” but it seems that some scientific theories are more like
junk than jewels.
But
isn't it at least correct that most scientific theories are true? No,
it isn't. Scientists love to churn out speculative theories,
particularly physicists and cosmologists. There are countless
different versions of what is called the cosmic inflation theory,
each making different assumptions. Presumably no more than one of
these different versions can be true. There are countless other
scientific theories describing different variations of the Big Bang,
different configurations of our universe, and different eventual
fates for our universe. Probably the great majority of these are
false. There are countless different attempts to describe a physics
beyond the Standard Model. The great majority of these theories must
be wrong, as they all make assumptions that conflict with each other.
A similar thing probably holds true about theories in fields such as
neurology and psychology.
I may
note that there is absolutely no ethic in science that a scientist
should regard a theory as being probably true before he publishes a
paper suggesting it. Quite to the contrary, there is a “publish or
perish” ethic under which it is considered just fine to publish a
paper suggesting some oddball theory that probably isn't true,
particularly if it is mathematically interesting or is an interesting
twist on some other theory or if it is an idea that somehow might
cause someone to think of a theory that is probably true. When
Harvard professor Abraham Loeb came up with an extremely implausible
but interesting and innovative theory about life evolving in the
first few million years of the universe's history, his colleagues
probably thought it was nice work.
But
is it true that we can tell that some scientific idea is solid when
it is called a theory? No, it isn't. The claim that scientists only
use the word “theory” for well-established ideas with lots of
evidence behind them is pure bunk, a groundless piece of folklore
typically trotted out when making the case for some theory that has
insufficient evidence behind it. What proves this is that the
completely unsubstantiated set of ideas called “string theory” is
referred to under just that name by scientists and non-scientists,
not some other name such as “string hypothesis.” Scientists
pretty much use the word “theory” just like ordinary people use
it.
But
is it true, as Zimmer claims, that in the world of science “theories
are neither hunches nor guesses”? As a general claim about
scientific theories, that is false. A sizable fraction of modern
scientific theories are highly speculative theories largely
consisting of guesses. In fact, many scientific theories are guesses
piled up on top of other guesses. When the cosmic inflation theory
was introduced, it was a wild guess about details of the first second
of the universe, which was built upon other wild guesses about the
universe (a class of speculative theories called grand unification
theories). Neither of these wild guesses has been confirmed, but the
cosmic inflation theory is still influential. Heaping speculations
upon speculations is typical behavior for the modern theoretical
physicist.
Zimmer's
generalizations about scientific theories are about as accurate as
generalizations such as, “You get quick service when you phone
technical support,” and “Middle age men are trim and muscular.”
Zimmer claims that in science, it's never “just a theory,” but
the truth is in science, it's very, very frequently “just a
theory.”
Do
any of the theories of science deserve to be called “crown jewels,”
the term so carelessly used by Zimmer as a general characterization
of scientific theories? Yes, but only a small few. The scientific
theories that are “crown jewels” are mainly those that make exact
numerical predictions that have been repeatedly proven to be true.
Some examples I can think of are the theory of gravitation, the theory
of electromagnetism, and the kinetic theory of matter (particularly when it predicts the behavior of gases).
The
table below lists some different categories of scientific
truth-claims, distinguishing between well-supported claims and claims
that are not well-supported. Only the tiniest fraction of scientific
theories fall into the first category. What can be particularly
confusing is that a particular set of ideas called a scientific
theory may be what we can call a composite theory, meaning a theory
consisting of different types of truth claims, some being
well-supported and others being not well-supported.
Given
such composite theories, it may be quite hard to sort out whether
some, all or most claims in a scientific theory should be believed.
There is no reliable shortcut to evaluating most scientific theories.
You cannot simply rely on a scientific consensus, because there may
be strong sociological, ideological and “bandwagon” factors that
may cause a majority of scientists in some field to endorse a theory
which is not actually worthy of belief, or that contains some
unworthy parts. There is no substitute for rigorously analyzing the
individual truth claims that make up a scientific theory, and
evaluating each such claim in a critical light, demanding supporting
evidence for each claim, listening to opposing arguments, and
rejecting any part of a theory which is not well-supported by facts
or evidence.
It's
okay to be a nature fanboy, but don't be a science theory fanboy who
reverently receives the latest dubious theoretical claim floating on
gossamer threads of thought. Be someone who analyzes scientific theories in the same probing, questioning way that you might analyze
the truth claims of a salesman in a used car lot.
No comments:
Post a Comment