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conditions the theory is not a good approximation or is not valid at all. The
ball is then back in the theorists’ court. If an experiment disagrees with the
current theory, the theory has to be changed, not the experiment.
(2)Theories should both predict and explain. The requirement of predic-
tive power means that a theory is only meaningful if it predicts something
that can be checked against experimental measurements that the theorist
did not already have at hand. That is, a theory should be testable. Explana-
tory value means that many phenomena should be accounted for with few
basic principles. If you answer every “why” question with “because that’s the
way it is,” then your theory has no explanatory value. Collecting lots of data
without being able to find any basic underlying principles is not science.
(3)Experiments should be reproducible. An experiment should be treated
with suspicion if it only works for one person, or only in one part of the
world. Anyone with the necessary skills and equipment should be able to
get the same results from the same experiment. This implies that science
transcends national and ethnic boundaries; you can be sure that nobody is
doing actual science who claims that their work is “Aryan, not Jewish,”
“Marxist, not bourgeois,” or “Christian, not atheistic.” An experiment
cannot be reproduced if it is secret, so science is necessarily a public enter-
prise.
As an example of the cycle of theory and experiment, a vital step toward
modern chemistry was the experimental observation that the chemical
elements could not be transformed into each other, e.g. lead could not be
turned into gold. This led to the theory that chemical reactions consisted of
rearrangements of the elements in different combinations, without any
change in the identities of the elements themselves. The theory worked for
hundreds of years, and was confirmed experimentally over a wide range of
pressures and temperatures and with many combinations of elements. Only
in the twentieth century did we learn that one element could be trans-
formed into one another under the conditions of extremely high pressure
and temperature existing in a nuclear bomb or inside a star. That observa-
tion didn’t completely invalidate the original theory of the immutability of
the elements, but it showed that it was only an approximation, valid at
ordinary temperatures and pressures.
Self-Check
A psychic conducts seances in which the spirits of the dead speak to the
participants. He says he has special psychic powers not possessed by other
people, which allow him to “channel” the communications with the spirits.
What part of the scientific method is being violated here. [Answer below.]
The scientific method as described here is an idealization, and should
not be understood as a set procedure for doing science. Scientists have as
many weaknesses and character flaws as any other group, and it is very
common for scientists to try to discredit other people’s experiments when
the results run contrary to their own favored point of view. Successful
science also has more to do with luck, intuition, and creativity than most
people realize, and the restrictions of the scientific method do not stifle
individuality and self-expression any more than the fugue and sonata forms
A satirical drawing of an alchemist’s
laboratory. H. Cock, after a drawing
by Peter Brueghel the Elder (16th
century).
If only he has the special powers, then his results can never be reproduced.
Chapter 0Introduction and Review