Their achievement was
sufficiently unprecedented to attract an enduring group of adherents away from
competing modes of scientific activity. Simultaneously, it was sufficiently
open-ended to leave all sorts of problems for the redefined group of
practitioners to resolve. Achievements that share these two characteristics I
shall henceforth refer to as ‘paradigms,’ a term that relates closely to
‘normal science.’
To be accepted as a paradigm,
a theory must seem better than its competitors, but it need not, and in fact
never does, explain all the facts with which it can be confronted. “Truth
emerges more readily from error than from confusion.” When, in the development
of a natural science, an individual or group first produces a synthesis able to
attract most of the next generation’s practitioners, the older schools
gradually disappear. Those unwilling or unable to accommodate their work to it
must proceed in isolation or attach themselves to some other group.
The success of a
paradigm—whether Aristotle’s analysis of motion, Ptolemy’s computations of planetary
position, Lavoisier’s application of the balance, or Maxwell’s mathematization
of the electromagnetic field—is at the start largely a promise of success
discoverable in selected and still incomplete examples. Normal science consists
in the actualization of that promise, an actualization achieved by extending
the knowledge of those facts that the paradigm displays as particularly
revealing, by increasing the extent of the match between those facts and the
paradigm’s predictions, and by further articulation of the paradigm itself.
Finally, the Principia had
been designed for application chiefly to problems of celestial mechanics. How
to adapt it for terrestrial applications, particularly for those of motion
under constraint, was by no means clear. Presumably their techniques and those
of the Principia could be shown to be special cases of a more general
formulation, but for some time no one saw quite how.
Normal science is a highly
determined activity, but it need not be entirely determined by rules. That is
why, at the start of this essay, I introduced shared paradigms rather than
shared rules, assumptions, and points of view as the source of coherence for
normal research traditions. Rules, I suggest, derive from paradigms, but
paradigms can guide research even in the absence of rules.
The community’s paradigms,
revealed in its textbooks, lectures, and laboratory exercises. By studying them
and by practicing with them, the members of the corresponding community learn
their trade. They can agree in their identification of a paradigm without
agreeing on, or even attempting to produce, a full interpretation or
rationalization of it. In short, though quantum mechanics (or Newtonian
dynamics, or electromagnetic theory) is a paradigm for many scientific groups,
it is not the same paradigm for them all. A revolution produced within one of
these traditions will not necessarily extend to the others as well.
These hint what our later
examination of paradigm rejection will disclose more fully: once it has achieved
the status of paradigm, a scientific theory is declared invalid only if an
alternate candidate is available to take its place. The decision to reject one
paradigm is always simultaneously the decision to accept another, and the
judgment leading to that decision involves the comparison of both paradigms
with nature and with each other. Almost always the men who achieve these
fundamental inventions of a new paradigm have been either very young or very
new to the field whose paradigm they change.
In both political and
scientific development the sense of malfunction that can lead to crisis is
prerequisite to revolution. The new theory might be simply a higher level
theory than those known before, one that linked together a whole group of lower
level theories without substantially changing any. Today, the theory of energy
conservation provides just such links between dynamics, chemistry, electricity,
optics, thermal theory, and so on. A second class of phenomena consists of
those whose nature is indicated by existing paradigms but whose details can be
understood only through further theory articulation. The differences between
successive paradigms are both necessary and irreconcilable. The reception of a
new paradigm often necessitates a redefinition of the corresponding science.
Some old problems may be relegated to another science or declared entirely
“unscientific.” Since no paradigm ever solves all the problems it defines and
since no two paradigms leave all the same problems unsolved, paradigm debates
always involve the question: Which problems is it more significant to have
solved?
Far more clearly than the
immediate experience from which they in part derive, operations and
measurements are paradigm-determined. It is only after experience has been thus
determined that the search for an operational definition or a pure
observation-language can begin.
In so far as he is engaged in
normal science, the research worker is a solver of puzzles, not a tester of
paradigms. Though he may, during the search for a particular puzzle’s solution,
try out a number of alternative approaches, rejecting those that fail to yield
the desired result, he is not testing the paradigm when he does so. Instead he
is like the chess player who, with a problem stated and the board physically or
mentally before him, tries out various alternative moves in the search for a
solution. These trial attempts, whether by the chess player or by the
scientist, are trials only of themselves, not of the rules of the game. They
are possible only so long as the paradigm itself is taken for granted.
Therefore, paradigm-testing occurs only after persistent failure to solve a
noteworthy puzzle has given rise to crisis. And even then it occurs only after
the sense of crisis has evoked an alternate candidate for paradigm. In the
sciences the testing situation never consists, as puzzle-solving does, simply
in the comparison of a single paradigm with nature. Instead, testing occurs as
part of the competition between two rival paradigms for the allegiance of the
scientific community.
The difficulties of conversion
have often been noted by scientists themselves. Darwin, in a particularly
perceptive passage at the end of his Origin of Species, wrote: “Although I am
fully convinced of the truth of the views given in this volume . . .
, I by no means expect to convince experienced naturalists whose minds are
stocked with a multitude of facts all viewed, during a long course of years,
from a point of view directly opposite to mine. . . . [B]ut I look
with confidence to the future,—to young and rising naturalists, who will be
able to view both sides of the question with impartiality.” And Max Planck,
surveying his own career in his Scientific Autobiography, sadly remarked that
“a new scientific truth does not triumph by convincing its opponents and making
them see the light, but rather because its opponents eventually die, and a new
generation grows up that is familiar with it.”
Still, to say that resistance
is inevitable and legitimate, that paradigm change cannot be justified by
proof, is not to say that no arguments are relevant or that scientists cannot
be persuaded to change their minds. Though a generation is sometimes required
to effect the change, scientific communities have again and again been converted
to new paradigms.
Probably the single most
prevalent claim advanced by the proponents of a new paradigm is that they can
solve the problems that have led the old one to a crisis. When it can
legitimately be made, this claim is often the most effective one possible. In
the area for which it is advanced the paradigm is known to be in trouble. That
trouble has repeatedly been explored, and attempts to remove it have again and
again proved vain. “Crucial experiments”—those able to discriminate particularly
sharply between the two paradigms—have been recognized and attested before the
new paradigm was even invented.
The claim to have solved the
crisis-provoking problems is, however, rarely sufficient by itself. Nor can it
always legitimately be made.
If we can learn to substitute
evolution-from-what-we-do-know for evolution-toward-what-we-wish-to-know, a
number of vexing problems may vanish in the process.
A paradigm is what the members
of a scientific community share, and, conversely, a scientific community
consists of men who share a paradigm. The members of a scientific community see
themselves and are seen by others as the men uniquely responsible for the
pursuit of a set of shared goals, including the training of their successors. While
learning to identify forces, masses, and accelerations in a variety of physical
situations not previously encountered, the student has also learned to design
the appropriate version of f = ma through which to interrelate them, often a
version for which he has encountered no literal equivalent before.
The law-sketch, say f = ma,
has functioned as a tool, informing the student what similarities to look for,
signaling the gestalt in which the situation is to be seen.
Hiç yorum yok:
Yorum Gönder