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Extraordinary
Science;
Incommensurability of Scientific Paradigms
Don
L. Anderson
Seismological
Laboratory, California Institute of Technology,
Pasadena, CA 91125
dla@gps.caltech.edu
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“"...conventional
wisdom is difficult to overturn. After more than 20
years some implications of plate tectonics have yet
to be fully appreciated by isotope geochemists…
geologists and geophysicists."
“"A myth
is an invented tale, often to explain some natural phenomenon...which
sometimes acquires the status of dogma...without a sound
logical foundation. It is a dogma that has distorted
thinking about the Earth for decades. In science this
is an old story, likely to be repeated again, as the
defenders of conventional wisdom are seldom treated
with the same scepticism as the challengers of the status
quo...the dogma has been defended with false assertions,
defective data, misconceptions and misunderstandings,
and with straw-man arguments... The justification...boils
down to a statement of belief, an opinion, rather than
a deduction from observations."”
“"[scientists]
are reluctant to abandon cherished concepts they grew
up with and have vigorously defended during their education
and research careers."”
Richard L. Armstrong,
1991
The distinction
between myth and science is subtle2. Mythic
thinking places special emphasis on a selective conjecture,
based typically on the initial observation or explanation
of a phenomenon, which is thereafter given privileged
status over alternate interpretations. This also describes
a paradigm. In myths, phenomena are attributed to things,
substances or beings, usually unobservable, rather than
processes. Examples include gods, demons and fairies;
in science we have had aether, calorics, phlogiston,
sea people, strings and plumes. Concepts in geoscience
are often mythic2; fixity of continents,
fixity of oceanic islands, uniformitarianism, geosynclinal
theory (vertical tectonics), mantle plumes, mantle reservoirs,
undegassed lower mantle, and so on. Geomyths and
paradigms can focus thinking but can retard further
progress by diverting attention away from the real cause
of a phenomenon and dismissing contrary views. An abandoned
paradigm is easily recognized in hindsight as a myth,
or a collection of ad hoc stories; failures
of current conventional wisdom are not so obvious.
Myths and vague theories
are impossible to falsify. In fact, logicians have shown
that no theory can be falsified by data; observational
evidence cannot decide between conflicting myths or
paradigms. Data, logic, rational discourse, simplicity,
and good intentions–the essence of progress in
ordinary science–have little to do with the overthrow
of a popular faith-based paradigm, or myth3.
Some of the implications
of plate theory are still not fully appreciated: plates
are not really rigid, the mantle is not homogeneous
or entirely subsolidus, magma fracture and lithospheric
architecture control locations of volcanic chains,
plates organize mantle convection–not vice versa,
delamination of continental crust and subduction of
aseismic ridges create fertile streaks in the mantle,
recycling creates low melting point blobs and so on.
Some of these are simple reversals of cause and effect
from conventional wisdom. By dropping such adjectives
as homogeneous, uniform, rigid, undeformable and
well-stirred the plate paradigm explains many of
the features that were thought to be outside its purview.
But the words plate tectonics, plate, convection,
mantle, upper mantle and lithosphere mean
different things to different workers, and therein lies
the rub.
We are currently on the
cusp of a major paradigm shift in Earth sciences. Ideas
about continental growth and breakup, mantle structure
and dynamics, reference systems, geochemical reservoirs
and magma chemistry are changing; weaknesses and paradoxes
of the Standard Models of mantle geochemistry and geodynamics
are multiplying. Most of this is invisible in the flagship
publications, which document perceived progress and
consensus views rather than problems in reigning paradigms,
or, heaven forbid, questioning of conventional wisdom.
Peer review and editorial and funding policies–the
infrastructure of a paradigm–are effective in
trimming both tails off the Gaussian that represents
the allowable range of publishable wisdom. How do we
recognize and deal with an impending paradigm
shift–a scientific revolution4?
Philosophers of science4-6
analyze extraordinary science; the great intuitive leaps
that spice up the history of science. This is not deductive
science or even discovery science. Extraordinary
science consists of bold formulation of hypotheses,
which are then subjected to attempts to falsify them.
Thomas Kuhn4 saw the history of science as
a succession of paradigms that are pitted against one
another rather than against objective scientific truth.
The scientific method does not apply when conventional
wisdom starts to fall apart. Defenders of an existing
paradigm use their own ground rules and assumptions
to attack the new models3, and rational discourse
plays little role4-6. New conventional wisdom
requires new terms, new assumptions, and, quite often,
different people.
In the terminal
stages of a paradigm, scientists working on the
same problem are unable to communicate with each
other. The new ideas are not yet completely worked
out. It is hard to communicate concepts, and this
becomes even harder as a new worldview and new
language unfold. Research groups diverge in the
problems that they think are important to work
on. One group may be trying to count the number
of angels on the head of a pin, while the other
group has moved beyond angels and pins, which,
in their view, may not exist. This is called incommensurability.
Very few scientists
ever find themselves outside of the box labeled
conventional wisdom. For some reason,
a few scientists decide that "staying the
course" is not a good idea and is no longer
justified. Philosophers have argued that the rules
change or there are no rules when you have decided
that the "emperor has no clothes" and
that something entirely different is needed. How
does one decide when current views are completely
wrong? Clearly, one does not take a vote, or look
to peer review. |
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One clue is that the words paradox, enigma, surprising
result, problem, anomaly, crisis and unanticipated start
to show up more frequently in published papers7.
When paradoxes and complexities multiply it may be
time for a new paradigm. A certain amount of humility
and befuddlement is reflected in these words. However,
the arguments that are used to defend the status quo
in spite of overwhelming evidence to the contrary are
also telling; “most people believe…”, “truth,
like beauty we suppose, is in the eye of the beholder…”, “the
approximations–or the data–are not good
enough”, “…the effects are too small
to detect”, “…evidence to the contrary
does not disprove a theory”, and “do not
throw out the baby with the bath water”. Many
of the arguments are based on ignorance of the field
or on tradition; "I admit there are a lot of problems
with the hypothesis, but I'm going to stick with it
until something better comes along", “I
spent a lot of time trying to find alternatives…”,
and “we must point out, however, that many other
geophysicists have interpreted the available data as
supporting plume emplacement..”. Also, after
considering selected pieces of several strawman models,
but not any of the mature alternative models “based
on an unusually comprehensive interdisciplinary database,
we maintain that the plume model…explains better
the available evidence than any of the suggested alternative
models….”. This covers the range of rationalisations
to which the defenders of a faltering paradigm appeal.
Most productive scientific theories are simple, or as
simple as they need to be, and they explain more than
they assume. If every new observation results
in a new modification to the theory, and the theory becomes
more and more complex, more vague, less general, and
less testable, then it is time to reconsider the options.
Scientists
can debate different theories, but those who have different
worldviews talk past one another; they cannot a priori arrive
at agreement given their different theoretical languages
and assumptions. One group argues from the perspective
that the phenomena or object they are studying actually
exists, be it aether, phlogiston, caloric or plume,
and their job is to refine the details. The other group
knows that it is silly to think about processes as things.
They know about waves, oxidation, thermal vibrations,
intrusion, recycling, stoping–and about scaling relations such as homologous
temperature; they worry about self-consistency. They
are not ready to accept that approximations such as homogeneity, uniformity, steady-state, fixity,
linearity, elastic and Boussinesq capture
the essence of phenomenon such as mantle dynamics.
The defense discounts problems by saying all approximations
have limitations to reality or that falsified predictions
do not falsify a theory; they are assuming they have
a good approximation to reality, and that the thing
they have constructed in their minds actually exists.
But aether is not a good approximation to
EM theory no matter how many bizarre properties are
assigned to it. Ignoring pressure or entropy is not
an approximation to mantle convection, or any thermodynamic
cycle. We need to keep in mind that lithospheric stress
and fertility variations in the asthenosphere might
not be well approximated by rigid–or flexible–tubes
to the core. Even if our current ideas about crustal
growth, geochemical reservoirs and mantle dynamics
are correct, it is useful to remind ourselves of what
the philosophers say, and, perhaps, bring back the
paradigm of Multiple Working
Hypotheses.
References & Notes
- Armstrong, Richard L. 1991. The Persistent
Myth of Continental Growth, Austr. J. Earth Sci.,
38, 613-630
- Dickinson, William R. 2003. The Place
And Power Of Myth In Geoscience: An Associate Editor’s
Perspective, American Journal of Science, 303, 856
– 864
- Debate about a paradigm is different
than rational scientific discourse; it can get ugly,
viz.
http://www.mantleplumes.org/TopPages/GreatPlumeDebateTop.html
http://www.mantleplumes.org/TopPages/MagazineTop.html
http://www.mantleplumes.org/FUA.html
- Kuhn, Thomas, 1962. The structure
of scientific revolutions, University of Chicago
Press, Chicago.
- Lakatos, I. 1970. ‘Falsification
and the Methodology of Scientific Research Programmes’,
in Lakatos, I & Musgrove, A. (eds). Criticism
and the Growth of Knowledge. Cambridge University
Press, Cambridge.
- Feyerabend, Paul, 1975. Against
Method: Outline of an Anarchistic Theory of Knowledge
,New Left Books, London, 1975.
- Try combining these words with plume
or geochemistry in a Google search.
last updated 3rd
March, 2007 |