It has been maintained that there
is an important asymmetry between the
verification and the refutation of a theory in empirical
science. Refutation has been said to be
conclusive or decisive, while verification was claimed to be irremediably
inconclusive. … The falsity of [the theory] is indeed deductively inferable by modus tollens.
-- “The Falsifiability of Theories”,
in: Adolf Grünbaum, Collected Works, vol. I (2013), p. 62
That is basically because an empirical law is, in general, a universal: ∀x P(x). Given any ¬P(a), that is falsified. Whereas successive confirming instances, while perhaps
increasing one’s confidence in the hypothesized law, do not deductively entail
it. Nor need that fact be,
in practical terms, a mere quibble, in cases of an infinite domain: thus, a conjecture in number theory
might be verified for all values of n
up to a billion -- a trillion -- a googolplex -- yet still turn out to be
false. (Indeed, toy conjectures of
this sort are trivially easy to
dream up. E.g. “No integer is evenly
divisible by a googolplex.”)
Taking confirming instances ‘too seriously’, is the Fallacy of Affirming
the Consequent.
Grünbaum then, however, in a Duhemian vein, weighs in
against such modus-tollentic tyranny, with the observation that, in empirical
science, you are really assuming (ex hypothesi) not merely a theory, but (in
unspoken conjunction therewith) various Auxiliary Assumptions: and one or more of these, rather than
your pet theory, might be the ones to suffer the fury of the tollendum. Thus, “Isolated component hypotheses of far-flung theoretical
systems are not separately refutable
but only contextually disconfirmable”
(id., p. 63).
The same idea, more sociologically stated:
Typically a theory is abandoned, not because of recalcitrant
observations on their own, but because of these together with some, perhaps
quite complex, reasoning from them:
in the extreme case, the observations may all be quite well known
already, and all that is new is
the reasoning.
-- Michael Dummett, Truth and
other enigmas (1978), p. 409
… that falsity, not truth, is the
primary notion.
-- Michael Dummett, Truth and
other enigmas (1978), p. xl
~
It is seldom that a theory is decisively k.o.’d by a Popperian uppercut to its predictive jaw. Often the process happens slowly, like a river silting
up; there is no single Aha! moment
(or rather, Oy veh! moment). In science, as in life, sometimes love grows old and love grows
cold. As, assessing a certain
philosophical program:
The further one
goes down the reformist path, the more implausible the consequences of one’s
theory are likely to become, until
at some point the implausibility
of the consequences comes to
outweigh the initial attractiveness of the theory.
-- Scott Soames, Philosophical
Analysis in the Twentieth Century (2003), vol. I, p. 299
That gradual, einsickernd,
process of disenchantment, lacks the drama of Popperian refutation, or of
Kuhnian paradigm-shift; it is more
reminiscent of the dissatisfying phenomenon (if it even is one) of truth decay.
~
The history of science -- though not the historiography of science -- is littered
with once-flourishing theories that somehow just … faded, without necessarily
ever having been decisively confronted or refuted. It is no fun to research and write about these, since
(a) they are losers in the lottery (rightly or not), and scarcely known today (so that one’s potential readership is infinitessimal -- and indistinguishable from zero among working scientists); and
(b) there is seldom a clear-cut moral in the tale.
(a) they are losers in the lottery (rightly or not), and scarcely known today (so that one’s potential readership is infinitessimal -- and indistinguishable from zero among working scientists); and
(b) there is seldom a clear-cut moral in the tale.
The occasions on which one does get an insight into some
defunct theory tend to be
biographies of otherwise-great scientists -- e.g. Theodore Porter’s fine account of the (as we now reckon him)
statistician Karl Pearson, which must
needs notice that hero’s period of infatuation with, mm, ahh, … ether squirts (pas devant les
enfants!); or Thomas Hankins‘s of William Rowan Hamilton. Or, sometimes, a historian of science
rolls up his sleeve and deconstructs/resurrects some particular thread of experiment. As, Gerald Holton’s commendable study
of “Subelectrons and Presuppositions”, involving the “classic” Millikan
experiment, of which we all get a telescoped and sanitized version in high
school physics. The actual saga is
more anfractuous, and less rich with easily digestible lessons.
[Millikan] found himself working
with the wrong presupposition, but he knew how to rid himself of it
eventually. Millikan launched into
that work with the same energy and obstinacy as into his earlier work on the quantization of the charge
of the electron, yet with the opposite assumption.
-- Gerald Holton, The scientific
imagination (1978), p. 72
And re the related experiments of Felix Ehrenhaft:
There was never a direct laboratory
disproof of Ehrenhaft’s claims. …
Lorentz … remark[ed]: “The
question cannot be said to be wholly elucidated.” In his review of the case, R.
Bär noted …: “the experiments left, at the very least, an uncomforable feeling.” Like
most such controversies, this one also faded into obscurity, without anything
as dramatic as a specific, generally agreed-upon falsification taking place
at all. Indeed, Ehrenhaft continue
to publish on subelectrons into the 1940s, long after everyone else had lost
interest in the matter.
-- Gerald Holton, The scientific
imagination (1978), p. 79
And that, within (central, classical) physics. The less
rigorous (natural and social) sciences
are much pocked with such as well.
~
Science, not as logically
implying some new phenomenon (such as the gravitational bending of light),
but as suggesting likely places to look. Thus:
The search, which has proved so
successful, for chemical atoms
having specific nuclear and electronic constitutions, and for chemical
molecules having specific atomic constitutions, has been stimulated by the
previous construction of theories to explain the consitution of atoms or of
molecules already known, theories which had, as it were, ‘gaps’ in them.
-- Richard Braithwaite, Scientific
Explanation (1953), p. 70
And indeed, not only the existence
of, say, atoms or isotopes with a given atomic weight and atomic number are thus -- not exactly ‘predicted’ in
the deductivist sense, but pointed to
-- but additionally, we shall expect certain behaviors, or ranges of behaviors,
based upon the place in the periodic table of that species (should it exist).
Thus, when the eka-aluminum
that Mendeleev hypothesized was
eventually identified (by a Frenchman, who thus had naming-rights and called it
gallium) and turned out to have
behavioral values very close to those predicted, while not proving
the theory of atomic chemistry as it then stood, was still much more than just
one more danged black raven.
[A footnote on another such predicted
discovery, that nicely illustrates consilience in the sciences, combining both
forefront atomic physics and
practical geology:
At the time Bohr was developing his
theory, the element following lutecium was undiscovered. But Bohr … asserted that, in this
unknown element, the added electron would have to be placed in the level n = 5. This would imply that the unknown
element would have an electronic configuration analogous to that of
zirconium. Inasmuch as elements that are chemically
analogous are usually found in the
same minerals, Bohr claimed that the missing element should be sought in
minerals containing zirconium. It
was indeed in such ores that the missing element, called hafnium [after the Latin name of Bohr’s hometown] was detected.
-- A. D’Abro, The Rise of the
New Physics (1939), p. 549. ]
This “guiding-light” role of a theory, not being a formal entailment, is likewise not subject to modus tollens (though of course it might
be abandoned in the face of an accumulation
of recalcitrant instances):
Whereas discovery of observable
properties which fill such gaps in a theory is rightly thought to provide a weighty confirmation of the theory … failure to discover such properties would not be regarded as
weighing against the theory, except
perhaps in very special cases.
-- Richard Braithwaite, Scientific
Explanation (1953), p. 70
No comments:
Post a Comment