Open Journal of Philosophy
2013. Vol.3, No.2, 351-357
Published Online May 2013 in SciRes (http://www.scirp.org/journal/ojpp) http://dx.doi.org/10.4236/ojpp.2013.32053
Scientific Prediction in the Beginning of the “Historical Turn”:
Stephen Toulmin and Thomas Kuhn
Wenceslao J. Gonzalez
Department of Humanities, University of A Coruña, Spain
Received January 14th, 2013; revised February 17th, 2013; accepted March 2nd, 2013
Copyright © 2013 Wenceslao J. Gonzalez. This is an open access article distributed under the Creative Com-
mons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, pro-
vided the original work is properly cited.
This paper considers the similarities and differences between Toulmin and Kuhn on the problem of pre-
diction. The context of the analysis is the beginning of the “historical turn” in philosophy of science (i.e.,
the period before the 1965 international colloquium held at Bedford College). The comparison between
these authors takes into account several levels: semantic, logical, epistemological, methodological, onto-
logical, and axiological. The main goal is to analyze whether there are influences of Toulmin in Kuhn re-
garding scientific prediction or, at least, if the former reached similar positions to the latter on the issue of
the role of prediction in science.
Keywords: Toulmin; Kuhn; Scientific Prediction; Historical Turn; Similarities; Differences
Historical Context
The “historical turn” in the philosophy and methodology of
science is commonly attributed to Thomas Kuhn and Imre La-
katos. In addition, there are contemporary authors, such as Paul
Feyerabend, and later thinkers, such as Larry Laudan, who
developed a view on philosophy of science based on the con-
tributions of history of science. Before the “historical turn” was
well established, some specialists made analyses in favor of
this historiographic dimension: on the one hand, is the case of
Ludwik Fleck, who passed almost unknown in the mid-thir-
ties;1 and, on the other hand, is the case of Norwood Russell
Hanson and Stephen Toulmin, who were more influential but
did not get the “turn” that Kuhn achieved later on.
Stephen Toulmin and Thomas Kuhn:
Some Similarities
Toulmin has some similarities with the author of The Struc-
ture of Scientific Revolutions (Kuhn, [1962b], 1970a). (i) In
Philosophy of Science (Toulmin, 1953) and in Foresight and
Understanding (Toulmin, 1961) he emphasizes the role of lan-
guage in science. Toulmin receives the direct influence of
Ludwig Wittgenstein, a thinker who also has repercussions in
Kuhn’s approach (mainly in his pragmatic view of the meaning
of scientific terms). (ii) They agree that the structure of scien-
tific theories is no longer a logical structure of the kind ac-
cepted by the logical positivists (or even by Karl Popper). (iii)
For Toulmin and Kuhn, epistemological factors are not a con-
struction like a building (from foundations on) but rather a
dynamic interaction with the social environment or historical
context. (iv) Methodologically, both thinkers take into account
the role of prediction as a guarantee of the validity of scientific
knowledge. (v) Ontologically, they see science as a human
activity rather than as an abstract amount of impersonal
knowledge. (vi) Axiologically, they recognize the importance
of the aim of scientific prediction, although they do not con-
sider it from a predictivist approach (like Hans Reichenbach
did in 1938 with Experience and Prediction), (cf. Reichenbach,
1938; see Gonzalez, 1995: pp. 35-56).
Within this historic-systematic context, the paper pays atten-
tion to the similarities and differences between Toulmin and
Kuhn on the problem of prediction. The comparison takes into
account the levels pointed out: semantic, logical, epistemologi-
cal, methodological, ontological, and axiological. The analysis
will focus on the beginning of the “historical turn,” i.e., the
period before the 1965 international colloquium in philosophy
of science held at Bedford College. The main goal is to analyze
whether there are influences of Toulmin on Kuhn regarding
scientific prediction or, at least, if the former reached similar
positions to the latter on the issue of the role of prediction in
science.
A Comparative Analysis on Prediction:
Toulmin and Kuhn
In 1961 Toulmin emphasized the connection between history
of science and philosophy of science.2 He wrote: “the critical
questions which a philosopher brings to science need to be
co-ordinated with the factual studies of history.”3 This was
written before Kuhn’s historiographic book was published,
2 “My debts to the working historians of science are so obvious as not to
require detailed acknowledgme n t,” Toulmin (196 1) , p. 5.
3 Toulmin (196 1), p. 16. “I have aimed (...) at sh owing the fascinating prob-
lems that arise when one brings logical and philosophical questions to bear
on the history of our scientific ideas,” Foresight and understanding:An
inquiry into the aims of science, p. 94.
1 An interesting comparison between Fleck’s views and Kuhn’s approach is
in Mößner (2 011), pp. 36 2-371.

W. J. GONZALEZ
where he defends a key role for history of science, which leads
to the philosophic-methodological categories of “normal sci-
ence” and “scientific revolution.”4
Semantics of Prediction
According to Toulmin, “words like ‘prediction’ (...) conceal
hidden ambiguities” (Toulmin, 1961: p. 16). Moreover, he
makes explicit that, in his judgment, “the word ‘prediction’ is
in fact a very slippery one. It slides between two extreme uses:
one naive, the other sophisticated. In its most obvious and ap-
pealing sense, explaining and predicting are emphatically not
all-of-a-piece; but, by hedging the term around with sufficient
qualifications, we can at least use it to provide a definition of
explanation” (Toulmin, 1961: p. 23).
Initially, following the Wittgensteinian influence — a prag-
matic account on language —, Toulmin considers that the
terms such as “prediction” or “predictive” can be understood in
the familiar, non-philosophical sense. This means that there are
“pre-dictions, fore-tellings, say ings-in-advance” (Toulmin, 1961:
p. 24). In addition, he does not distinguish between “foresight,”
“prediction,” and “forecasting,” which — in my judgment —
should be done in order to analyze the foretellings in terms of
the different degree of control of the variables. This possibility
is more relevant in economics than in other sciences (cf. Gon-
zalez, 1996b: pp. 201-228; especially, pp. 215-216).
But Toulmin embraces de facto another position: prediction
as testable implication. This involves “the ability to infer the
occurrence of any event in question — whether it has already
happened, is happening now, or is going to happen in the fu-
ture” (Toulmin, 1961: p. 27). Thus, the distinction between
“pre-diction” (saying beforehand that something is going to
happen) and “retro-diction” (inferring after the event it has
happened) is diluted. This seems to me a mistake, insofar as the
future is epistemologically and ontologically related to some-
thing with a wide range of possibilities, which is far wider —
and, eventually, more complex — than the past.
On analyzing Toulmin’s texts it seems that his semantics of
science includes three different uses of predictions: a) future
phenomena that are already confirmed, due to some kinds of
laws (e.g., eclipses); b) future events not yet confirmed that are
themselves still in the future (Toulmin, 1961: p. 26); and c) past
things to be discovered (e.g., in paleontology), (cf. Toulmin,
1961: pp. 26-27). Therefore, he offers us a very confused no-
tion of “prediction:” ‘predictive success’ can “cover inferences
about events at any time — past, present, or future — whether
we eventually observe the event itself or only its after-effects”
(Toulmin, 1961: p. 27).
Kuhn initially uses “prediction” with the common meaning
of something said in advance, be the novelty “expected” or
“unexpected” (cf. Kuhn, [1962b], 1970a: p. 35). Thus, it is
connected to the idea of “anticipation” rather than to looking
back: prediction means — in principle — “foreknowledge,”5
which makes a genuine “retrodiction” really hard. But, to a
large extent, it is a “contextual meaning:” prediction depends
on a content that vies for the allegiance of the scientific com-
munity,6 within a paradigm that it is historically supported and
can be changed any time. This is one of the roots of Kuhn’s
relativism of his initial philosophic-methodological period.7
Another semantic distinction in Kuhn, that has epistemo-
logical and methodological consequences, is the difference
between “quantitative predictions” and “qualitative predic-
tions.” This distinction is reinforced in Postscript-1969, where
he gives more relevance to the former than to the latter: “quan-
titative predictions are preferable to qualitative ones” (Kuhn,
1970b: p. 185). Previously, he has pointed out that quantitative
predictions have had a key role in history of science, such as in
Newton’s success in predicting astronomical observations (cf.
Kuhn, [1962b], 1970a: p. 154) or in the acceptance of Ein-
stein’s general theory of relativity.8
The Structure of Scientific Theories and Prediction
From a structural point of view, Toulmin considers that sci-
entific theories can have different orientations: “science is cer-
tainly not a matter of forecasting alone, since we also have to
discover explanatory connections between the happening we
predict” (Toulmin, 1961: p. 16). Thus, he criticizes vehemently
the predictivist thesis9 (i.e., an instrumentalism on prediction),
maybe because he held it before Foresight and Understanding.
In this book, he rejects that the purpose of an explanatory sci-
ence is to lead to predictions and that the merits of a scientific
theory are in proportion to the correct predictions that it implies
(cf. Toulmin, 1961: pp. 22-23).
To begin with, Toulmin considers that explanatory power
cannot be defined in terms of forecasts. He highlights that
“plenty of powerful theories have led to no categorical, verifi-
able forecasts whatever. One obvious example is Darwin’s
theory, explaining the origin of species by reference to varia-
tion and natural selection. No scientist has ever used this theory
to foretell the coming-into-existence of creatures of a novel
species, still less verified his forecasts. Yet many scientists
have accepted Darwin’s theory as having great explanatory
power” (Toulmin, 1961: pp. 24-25).
It seems that, for Toulmin, there is a structural distinction in
science between the realm of “explanation” (i.e., explanatory
power) and “prediction” (i.e., predictive success), where the
former is good enough to have “acceptable science.” In the case
of Darwin’s ideas, he maintains that “actual forecasting became
possible only with the development of modern ecology and
genetics, yet men did not wait for this before recognizing the
explanatory merits of the theory of natural selection” (Toulmin,
1961: p. 26).
However, for Toulmin, a quite different case could also be
possible: a predictive success without an adequate explanatory
conception. Historically, “the Babylonians acquired great fore-
casting-power, but they conspicuously lacked understanding.
To discover that events of a certain kind are predictable —
even to develop effective techniques for forecasting them — is
evidently quite different from having an adequate theory about
7 On the different stages of Kuhn’s philosophic-methodological ap
p
roach, cf.
Gonzale z (2004a), pp. 15-103.
8 The equations of Einstein’s general theory of relativity have yielded three
p
redictions that can be compared with observatio n: “the deflection of light in
the sun gravitational field, the precession of the perihelion of Mercury, and
the red shift of light from distant stars. Only the first two are actually quan-
titative predictions in the present state of the theory,” Kuhn ([1961a], 1977),
p. 188, n.
9 “Osiander provides a cl assic statement of the predictiv ist thesis,” Toulmin
(1961), p. 41.
4 Cf. Kuhn ([1962b], 1970a), ch. 1, pp. 1-7. “History (...) could produce a
decisive transformation in the image of science by which we are now pos-
sessed,” Kuhn ([1962b], 1970a), p. 1.
5 Cf. Kuhn ([ 1962a], 197 7), pp. 165-177; especially, p. 167.
6 Cf. Kuhn ([ 1961a], 197 7), pp. 178-224; especially, p. 200.
352

W. J. GONZALEZ
them, through which they can be understood” (Toulmin, 1961:
p. 30).
Given his special interest in trying to show the predictivist
thesis as mistaken, Toulmin goes very far in his analysis of
prediction, because he conceives “scientific prediction” as di-
luted in the “explanatory power” of a theory or in the task of
“making sense of” a phenomenon. Thus, for him, the term
“prediction” can mean the same as “explanatory inference” or
“prediction” could be a simple “forecast” that is only one test
of the explanatory power of a theory (and it is neither a neces-
sary nor a sufficient one), (cf. Toulmin, 1961: p. 35). Toulmin’s
mistake is in seeing prediction as a pure instrument, a mere
application or “technique” without a real content of its own.
Meanwhile Kuhn’s structure of scientific theories — mainly
in his first philosophical approach — is focused on two
well-known categories: “normal science” and “scientific revo-
lution.” In normal science prediction appears within a small
class of factual determinations of paradigms: “A part of normal
theoretical work, though a small part, consists simply in the use
of existing theory to predict factual information of intrinsic
value. The manufacture of astronomical ephemerides, the com-
putation of lens characteristics, and the production of radio
propagation curves are examples of this sort.”10 In this regard,
the important thing is to increase both the scope and precision
of scientific research.
When the analysis moves towards “scientific revolutions”
the relation between prediction and “discoveries” (or novelties
of fact) appears as well as the nexus between prediction and
“inventions” (or novelties of theory), (cf. Kuhn, [1962b], 1970a:
p. 52). In the case of discoveries, Kuhn maintains that “the
paradigms subscribed to by Roentgen and his contemporaries
could not be used to predict X-rays.”11 Thus, a feature of
Kuhnian “extraordinary research” is the novelty introduced by
the new paradigm that “permits the prediction of phenomena
that had been entirely unsuspected while the old one prevailed”
(Kuhn, [1962b], 1970a: p. 154).
Epistemology of Prediction
Epistemologically, prediction is not — for Toulmin — re-
duced to knowledge about a possible future event. He considers
“prediction” as an “assertion about the occurrence of a particu-
lar sort of event — whether in the past, present, or future”
(Toulmin, 1961: p. 31). In addition, scientific knowledge can
be used either in “categorical predictions” (‘a total eclipse of
Moon will be on ...’) or in “hypothetical and conditional pre-
dictions” (‘if specified conditions are fulfilled, such and such
event will happen’ or ‘a given event happened in the past will
occur again if and whenever such and such antecedent condi-
tions hold’), (cf. Toulmin, 1961: p. 31).
This distinction categorical-conditional or hypothetical pre-
dictions has methodological consequences, because Toulmin
thinks that the method for testing scientific theories depends on
the ability to make conditional predictions rather than cate-
gorical predictions. He uses the historical case of the Babylo-
nians, where “categorical predictions are relatively unimportant
as a test of the explanatory power of a scientific theory, since
we may discover how to forecast by simple trial-and-error,
without any understanding of the processes involved” (Toulmin,
1961: p. 32).
Following this view, Toulmin rejects that commonly a scien-
tific theory is to be judged by the categorical forecasts to which
it leads. His conception is different: a theory is “to be judged by
the number of factual assertions (past, present or future, cate-
gorical or hypothetical) which it supports” (Toulmin, 1961: p.
34). He considers that this position can be seen in the example
of Newton’s theory. Furthermore, he conceives that “support”
here means “makes sense of” or “explains,” where the impor-
tant thing is not the empirical success of a prediction but rather
the task of offering an intelligible account of the phenomenon.
Although Kuhn uses also Newton’s theory as a key case for
prediction, it seems that he gives more relevance than Toulmin
to empirical success when there is a comparison between
Newton’s predictions and actual experiments. For Kuhn, the
problem of precision is particularly important (Kuhn, [1962b],
1970a: p. 31). Moreover, precision is — in addition to accuracy
— a central epistemological topic of The Structure of Scientific
Revolutions.12 Thus, he defends that “Newton’s success in pre-
dicting quantitative astronomical observations was probably the
single most important reason for his theory’s triumph over its
more reasonable but uniformly qualitative competitors” (Kuhn,
[1962b], 1970a: p. 154).
Nevertheless, when Kuhn analyzes the famous case of para-
digm change — the emergence of Copernican astronomy —, he
is cautious about “predictive success.” He recognizes that the
Ptolemaic system “was admirably successful in predicting the
changing positions of both stars and planets. No other ancient
system had performed so well; for the stars, Ptolemaic astron-
omy is still widely used today as an engineering approximation;
for the planets, Ptolemy’s predictions were as good as Coper-
nicus’. But to be admirably successful is never, for a scientific
theory, to be completely successful. With respect both to plan-
etary position and to precession of the equinoxes, predictions
made with Ptolemy’s system never quite conformed with the
best available observations” (Kuhn, [1962b], 1970a: p. 68).
Therefore, Kuhn does not endorse here an instrumentalist
position. He is not in favor of a predictivist thesis where scien-
tific knowledge should be subordinated to a mere precision or
pure accuracy of predictions. He is clear enough when he says
that “Copernicus’ theory was not more accurate than Ptolemy’s
and did not lead directly to any improvement in the cale ndar .”13
The difference is in the new “paradigm,” because it permits the
prediction of new phenomena. But Kuhn goes too far when he
links it to “incommensurability,” insofar as he holds that, the
difference in their predictions (in scientific revolutions), could
not occur if the two were logically compatible (cf. Kuhn,
[1962b], 1970a: p. 97).
Methodol ogy of Prediction
Insofar as science has not — for Toulmin — one aim but
many, then its development passes through many contrasted
stages. Methodologically, he emphasizes several aspects. (i) It
is fruitless to seek a single, all-purpose “scientific method,”
10 Kuhn ([1962b], 1970a), p. 30. On the three normal foci for factual scien-
tific investigation, cf. Kuhn ([1962 b], 1970a), pp. 25-34.
11 Kuhn ([1962b], 1970a), p. 58. “Maxwell’s electromagnetic theory had not
yet been accepted everywhere, and the particular theory of cathode rays was
only one of several current speculatio n s,” Kuhn ([1962b], 1970a), p. 58.
12 Cf. Kuhn ([1962b], 1970a), pp. 25-26, 30-31, 36, 42, 52, 153-155, 170,
185 and 199.
13 Kuhn ([1962b], 1970a), p. 154. “Until Kepler, the Co
p
ernican theory
scarcely improved upon the predictions of planetary position made by
Ptolemy ,” Kuhn ([1962b], 1970a), p. 156.

W. J. GONZALEZ
because science is a human activity that calls for a broad range
of different enquires. (ii) There is growth and evolution of sci-
entific ideas that do not depend on a unique method. The diver-
sity of its methods evolves by variation and selection (cf.
Toulmin, 1961: p. 17).
Nevertheless, Toulmin sees prediction in instrumental terms:
it appears in Foresight and Understanding as a tool or mathe-
matical technique. Due this methodological characteristic, a
disconnection is possible in science between explanation (or
“understanding”) and prediction: “the mathematical techniques
used to predict the times and heights of tides, the motions of
heavenly bodies, and so on. Yet (as reflection reminds us) some
of the most successful techniques for making such predictions
have largely lacked the power to explain the events so forecast,
having been worked out by trial-and-error and without any
theoretical basis; whereas some respectable theories about the
very same natural happenings have been predictively almost
entirely fruitless” (Toulmin, 1961: p. 27).
Again, this instrumental view leads Toulmin to further con-
fusion: to blur the conceptual distinction between science and
technology . He claims that forecast ing “is a craft or technol ogy
[sic], an application of science rather than the kernel of science
itself. If a technique of forecasting is successful, that is one
more fact, which scientists must try to explain, and may suc-
ceed in explaining. Yet a novel and successful theory may lead
to no increase in our forecasting skill; while, alternatively, a
successful forecasting-technique may remain for centuries
without any scientific basis” (Toulmin, 1961: p. 36).
Methodologically, prediction is in Kuhn connected to the
success of a paradigm, (cf. Kuhn, [1962b], 1970a: pp. 23-24).
The advancement of science is made “by increasing the extent
of the match between those facts and the paradigm’s predic-
tions” (Kuhn, [1962b], 1970a: p. 24). Thus, it seems that the
Kuhnian success of a paradigm through predictions has simi-
larities with the Lakatosian progress of scientific research pro-
grams through prediction of novel facts (cf. Gonzalez, 2001).
There are two aspects similar to Lakatos’s approach: 1) a gen-
uine scientific advancement is made when predictions lead to
novel facts, and 2) anomalies are not a crucial factor for ques-
tioning a scientific c on tr ib ution when predictions are involved.
These aspects — the relevance of prediction of novel facts
and the secondary role of anomalies — can be found in Kuhn’s
texts. a) In some cases, discoveries “like the light spot at the
center of the shadow of a circular disk, were predictions from
the new hypothesis, ones whose success helped to transform it
to a paradigm for later work” (Kuhn, [1962b], 1970a: p. 89). b)
A “persistent and recognized anomaly does not always induce
crisis. No one seriously questioned Newtonian theory because
of the long-recognized discrepancies between predictions from
that theory and both the speed of sound and the motion of
Mercury.” (Kuhn, [1962b], 1970a: p. 81).
When Kuhn offers his characterization of “The Historical
Structure of Scientific Discovery,” he distinguishes two main
kinds of discoveries: (i) “those discoveries — including oxygen,
the electric current, X rays, and the electron — which could be
predicted from accepted theory in advance and which therefore
caught the assembled profession by surprise” (Kuhn, [1962a],
1977: p. 166), and (ii) those discoveries — the neutrino, radio
waves, and the elements which filled empty places in the peri-
odic table — where the existence of the objects “had been pre-
dicted from theory before they were discovered, and the men
who made the discoveries therefore knew from the start what to
look for” (Kuhn, [1962a], 1977: p. 167). This connection be-
tween prediction and discovery is used by Kuhn to point out the
teleological character of the research in those cases: the fore-
knowledge provided criteria that told scientists when their goal
had been reached (cf. Kuhn, [1962a], 1977: p. 167).
Prediction as a Human Activity (Ontology of
Prediction)
Prima facie, ontology of prediction can be seen in two ways,
according to the focus of the analysis: on the one hand, the
phenomena that are predicted (as we know, for Toulmin, they
could be past, present or future); and, on the other hand, the
process itself of predicting, which involves a characterization
of science as a whole. In this regard, due to a Wittgensteinian
influence,14 Toulmin sees science as a human activity rather
than an abstract or timeless content, and conceives it as a mul-
ti-purpose activity (cf. Toulmin, 1961: p. 18). Moreover, he
thinks that the entire range of its activities cannot be encom-
passed in a single phrase.
Ontologically, prediction as scientific process appears in the
context of a human practice. For Toulmin, prediction is based
on a “craft” that began on a purely empirical basis, by trial and
error, and this happened before its success could be accounted
for scientifically. Thus, he distinguishes “scientific predictions
and techniques from pre-scientific forecasts and crafts. Any
craft may simply be successful as a matter of experience; or
alternatively, its efficacy may be intelligible in terms of our
general ideas about Nature.” (Toulmin, 1961: p. 37). This
means that he is not paying real attention to social sciences.
Even though Toulmin emphasizes the importance of history
of science and the difference between the historical periods, his
philosophy of science highlights the internal factors of scien-
tific activity. For him, the central aims of science lie in the field
of intellectual creation. Thus, other activities — such as pre-
dicting — “are properly called ‘scientific’ from their connec-
tion with the explanatory ideas and ideals which are the heart of
natural science” (Toulmin, 1961: p. 38). In this regard, a few
years later, Toulmin criticizes Kuhn’s views on the distinction
between normal and revolutionary science. He wants to em-
phasize that “any attempt to understand the nature of intellec-
tual development in science must, surely, be to distinguish
between the intellectual authority of an established conceptual
scheme and the magisterial authority of a dominant individ-
ual.”15
Both normal science and scientific revolutions are, for Kuhn,
“community-based activities” (Kuhn, 1970b: p. 179). Among
these activities is predicting. This activity has — for him — a
particular interest, insofar as the possible knowledge and fore-
knowledge has more weight than the knowledge that we actu-
ally possess, (cf. Kuhn, [1962b], 1970a: p. 171). In this regard,
paradigm predictions contribute to the world-view. They have
more relevance in scientific revolutions than in normal science,
because “no part of the aim of normal science is to call forth
new sorts of phenomena” (Kuhn, [1962b], 1970a: p. 24).
Predictive success as such is not, for Kuhn, the main aim of
scientific activity of predicting. Thus, he is against an instru-
mentalist vision of prediction: “to be admirably successful is
never, for a scientific theory, to be completely successful”
14 On Wittgenstein’s views on science and prediction, cf. Gonzalez (1996a),
pp. 299-332.
15 Toulmin (1970), p. 40. This paper was originally delivered in 1965.
354

W. J. GONZALEZ
(Kuhn, [1962b], 1970a: p. 68). What matters, for him, is that
predictions made could be conformed with the best available
observations (cf. Kuhn, [1962b], 1970a: p. 68). This seems a
realistic element in Kuhnian analysis, where scientific predic-
tion is not a mere “technique.” The world-view can be more
precise through prediction and, in addition, scientific prediction
can enlarge our vision of the world when the new paradigm
leads to phenomena that did not appear in old paradigms (cf.
Kuhn, [1962b], 1970a: p. 154).
Axiology of Research and Prediction
For Toulmin, it is clear that science has performed manifold
functions. It performs now and might perform in future, within
the whole intellectual economy (cf. Toulmin, 1961: p. 15).
Thus, he criticizes the attempts made by philosophers to offer
characterizations of science where one requirement, such as
predictive success, appears as the unique test of a scientific
hypothesis. He rejects this possibility: “one cannot hope to get
any real understanding from such a nutshell answer. There is no
universal recipe for all science and all scientists” (Toulmin,
1961: p. 15). This pluralism about aims involves a diversity of
values.
Within the historical context of the beginning of the 1960’s,
Toulmin offers a quite different approach from the logical em-
piricist (and, especially, distant from Reichenbach’s predictiv-
ism) and also diverse from Popper’s conception (insofar as he
is very critical with the role of “prediction” in science).16 But
Toulmin does share with them the primacy of internal aims of
science over the external elements (social, cultural, etc.). For
him, “the central aims of science (...) lie in the field of intellec-
tual creation” (Toulmin, 1961: p. 38). They are “concerned
with a search for understanding — a desire to make the course
of Nature not just predictable but intelligible — and this has
meant looking for rational patterns of connections in terms of
which we can make sense of the flux of events” (Toulmin,
1961: p. 99). Thus, for him, “prediction is all very well; but we
must make sense of what we predict” (Toulmin, 1961: p. 115).
Even in Kuhn, internal values (epistemological, methodo-
logical, etc.) are more important in scientific activity than ex-
ternal values (social, cultural, etc.). Moreover, a few years after
his famous book, in Postscript-1969 he emphasized the axiol-
ogy of research based on prediction when he wrote: “probably
the most deeply held values concern predictions: they should be
accurate; quantitative predictions are preferable to qualitative
ones; whatever the margin of permissible error, it should be
consistently satisfied in a given field; and so on” (Kuhn, 1970b:
p. 185).
Regarding the values themselves in scientific predictions,
Kuhn highlights the increase of scope and precision of research
(cf. Kuhn, [1962b], 1970a: p. 30). But there is not — for him
— a central value such as “truth” or an ultimate goal of scien-
tific activity. He rejects the idea of science as a process of evo-
lution toward anything. Thus, he claims “if we can learn to
substitute evolution-from-what-we-do-know for evolution-to-
ward-what-we-wish-to-know, a number of vexing problems
may vanish in the process” (Kuhn, [1962b], 1970a: p. 171).
Therefore, for Kuhn, prediction — as well as any other scien-
tific value — is not an objective value, insofar as in The Struc-
ture of Scientific Revolutions the possibility of an objective
account of nature or a process that can bring us closer to an
ultimate goal such as truth is dismissed (cf. Kuhn, [1962b],
1970a: p. 171).
Final Remarks
From the comparison between Toulmin and Kuhn on predic-
tion, it seems that the differences are more intense than the
similitudes. (i) Semantically, prediction has in Toulmin a more
vague and polysemous meaning than in Kuhn. This happens as
a consequence of the sense of prediction as a “testable implica-
tion” whose reference could be in the past, present or future;
whereas the Kuhnian approach connects the use of “prediction”
with anticipation of an event that, at least for the scientific
community, has a novelty and appears as a possible future
event.
(ii) Logically, the focus in the structure of scientific theories
is also diverse in both authors. Toulmin insists on the relation
between prediction and the traditional topics of explanation
(and “understanding”) of a scientific theory, whereas Kuhn
deals with prediction within his distinction “normal science”-
“scientific revolution,” which involves “paradigms” rather than
individual scientific theories that are seen from a linguistic
perspective.
(iii) Epistemologically, both thinkers are keen on evolution-
ary ideas,17 but scientific knowledge of prediction is considered
from two different angles: on the one hand, there is a particular
interest in Toulmin to discredit any predictivist approach on
prediction (statements that could be about past, present or fu-
ture events); and, on the other hand, there is a notorious em-
phasis in Kuhn on prediction as a key contribution to scientific
knowledge.
(iv) From a methodological point of view, both philosophers
of science shared that there is not a single, all-purpose “scien-
tific method,” because they see science as a human activity
open to a broad range of different enquires. The difference is in
Kuhn’s insistence on prediction as connected to genuine nov-
elty (i.e., future rather than past or present) and that prediction
can lead to discoveries. To some extent, his views connect to
Lakatos’s perspective on prediction and novel facts based on
historical cases of science.
(v) Ontologically, the scientific activity of predicting is to
some extent different in Toulmin and Kuhn. For the former,
prediction is an impersonal “craft” or “technique” (cf. Toulmin,
1961: p. 36); meanwhile, for the latter, prediction is developed
by the scientific community towards precision and accuracy.
The technique is an instrument to be inserted in an explanatory
context in order to “make sense” of the world, whereas the
Kuhnian emphasis on precision and accuracy, which highlights
quantitative predictions over qualitative ones, looks for a
genuine information on the world that has weight on its own.
(vi) Axiologically, prediction has a clearer value in Kuhn
than in Toulmin. But, due to the general approach of the phi-
losophic-methodological period of The Structure of Scientific
Revolutions, prediction appears as a value of a relativistic
framework. Toulmin does not go so far. His instrumentalism is
open to the value of truth: “science progresses, not by recog-
17 Evolutionary Epistemology — or at least a Darwinian influence on scien-
tific knowledge — is in both authors. “In the evolution of scientific ideas, as
in the ev olution of speci es, chan ge resu lts fr om the sel ective perpetu ation o
f
variants,” Toulmin (1961), p. 110. C f. Kuhn ([19 62b], 1970a ) , pp. 170-172.
16 Popper insists on the role of prediction within the general philosophy and
methodology of science, where he is very critical with prediction in the
realm of social sciences. Cf. Gonzalez (2004b), pp. 78-98.

W. J. GONZALEZ
nizing the truth of new observations alone, but making sense of
them” (Toulmin, 1961: p. 81).
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