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148 A Realist Theory of Science
2. THE SURPLUS-ELEMENT IN THE ANALYSIS OF
LAW-LIKE STATEMENTS: A CRITIQUE OF THE THEORY
OF MODELS
It has often been held that a constant conjunction
of events is not a sufficient condition for a causal law.
This may be because it is regarded as incapable of
sustaining the intuitively obvious
The Logic of Scientific Discovery 149
and important difference between necessary and accidental
sequences or in Johnson's time-honoured terminology
between universals of law' and `universals of fast'.4 Or
it may be because it is regarded as incapable of
licensing what it is intuitively felt causal laws do
licence, namely counter-factual conditionals.5 It is
never seriously denied that we feel, and scientists act
as if, some but not other sequences of events are
`necessarily connected'; so that we must possess the
concept. What the radical empiricist, in the form of
Hume, denies is: (a) that there is any objective basis
for this distinction, i.e. that it corresponds to any
real difference between the two sequences of events; and
(b) that there is any justification, apart from habit or
custom, for our ascriptions of natural necessity and
accident.6 Most philosophers since Hume have attempted to
show how he was wrong in (b) without objecting to (a). I
want to argue that Hume was wrong in (a); and that it is
only if we can establish this that we can show why he was
wrong in (b) also.
The radical empiricist challenge to philosophers
then is to provide an alternative account of the
`surplus-element'7 in the analysis of law-like
statements; that is, that element over and above the
(presumed) constant conjunction that explains our
ascriptions of necessity; and which will show how, and
the conditions under which, a distinction between
necessary and accidental sequences and the assertion of
counter-factuals can be rationally justified. The usual
response to this challenge consists in the attempt to
locate the surplus-element in the statement's
`explanation', and more particularly in the `theory'
which explains it. However the terms `explanation' and
`theory' cover a gamut of philosophical positions, which
must now be considered.
The deducibility of a law-like statement from a set
of higher order statements is often regarded as a
criterion of `explanation'.8
4 W. E. Johnson, Logic, Vol. III, Chap. 1.
5 R. Chisholm, `The Contrary to Fact Conditional', Mind
55 (1946), reprinted in Readings in Philosophical
Analysis, eds. H. Feigl and G. Maxwell, pp. 482-97.
6 (a) and (b) correspond of course to Hume's two
definitions of `cause'. See D. Hume, Treatise, p. 172
and Inquiry, pp. 76-7.
7 I owe this term of G. Buchdahl, op. cit., p. 27 and
passim.
8 See e.g. R. B. Braithwaite, op. Cit., Chap. 8;
C. G. Hempel, op. cit., Chap. 12; and E. Nagel, op. Cit.,
Chap. 4.
150 A Realist Theory of Science
However if deducibility is the only criterion for
explanation and the source of the surplus-element is its
explanation there will be an infinite number of
surplus-elements for *any* statement. Hence any statement
can be said to be law-like on an infinite number of
grounds!9 Deducibility alone cannot explicate the
distinction between necessary and accidental or nomic and
non-nomic universals. Moreover additional criteria such
as simplicity can only reduce the number of possible
explanations for a statement which has already been
identified as law-like. But they cannot be used to say
which statements are law-like and so possess the
surplus-element. For even if there were a simplest
explanation for every statement, there are no absolutely
simple explanations. Thus such criteria can at best be
used to explain why we choose one explanation rather than
another, but not why one statement rather than another is
regarded as law-like.10
Of course it might be objected that when everything
is explained all factual statements will be law-like.
But what would count as an explanation then? Could it
be anything other than an inexplicable constant
conjunction of events, as in the case of
9 The Jesuit mathematicism Clavius demonstrated this
fallacy in Osiander's apologetic preface to Copernicus'
De Revolutionibus. Osiander had argued, as Galileo was
later invited to before the Inquisition, that the
helio-centric theory was merely a mathematically adequate
representation of the facts of planetary motion that made
no claim to be true. Clavius pointed out that it was
never a good argument in favour of a theory that it
`saved the appearances', as a true result could be
derived from any number of absurd or false
premises. (Cf. J. Losee, An Historical Introduction to
the Philosophy of Science, pp. 44-5.) Indeed even if we
exclude all premises which we know to be false or which
are not explicitly defined there will still be an
infinite number of sets of premises from which the facts
can be deduced, provided we allow for the introduction of
artificial predicates such as Hesse's `tove'
(M. B. Hesse, Models and Analogies in Science, p. 30), of
which place- and time-dependent predicates such as
Goodman's `grue' (N. Goodman, Fact, Fiction and Forecast,
p. 74) merely form a special class. Hence deducibility
cannot provide a sufficient criterion for choosing one
set of premises rather than another (the source of
Goodman's paradox) or for justifying one statement rather
than another as law-like.
10 This is of course a very poor best. For (i) the
simplest of any small number of explanations is not
necessarily the best (cf. M. Bunge, The Myth of
Simplicity, pp. 51-134); (ii) there will still be an in
principle infinite number of equally simple explanations,
if we restrict ourselves to formal or syntactical
criteria alone (cf. J. J. Katz, The Problem of Induction
and its Solution, Chaps. 4 and 5).
The Logic of Scientific Discovery 151
Mill's unconditional laws?11 If it could not, we are back
with Hume, and have done nothing to allay the sting of the
radical empiricist challenge. If it could, some
alternative non-Humean analysis of the ultimate or
highest-order laws must be given which will show how
they, as uniquely qualified `explainers', do possess a
genuine surplus-element. We are thus faced with the
following dilemma: either explanation is achieved by
subsumption under higher-order laws in which case the
problem is merely shifted, for a surplus-element must be
found for them if they are to qualify as `laws'; or an
alternative analysis of `explanation' must be given,
which does not identify the explanans with a further set
of laws, and so provides room for the location of a
surplus-element in the analysis of laws, within the
context of their explanation, at any one level.
It might be thought that it is in the capacity of
the law-like statement to yield successful predictions
that the source of the surplus-element lies. But this
will not do without an analysis of the `capacity' or
`power'. For the Humean it is the past and actual
successes of the statement that count, not its potential
ones. And these can at best explain, not justify, the
surplus-element. It is the surplus-element that must
provide our inductive warrant, if we have one: rather
than the other way round. Moreover even an accidental
generalization is capable of yielding correct
predictions, viz. as long as the conditions that account
for it persist. This suggests that, even if we were to
possess some general inductive warrant, predictive
success alone could not differentiate necessary from
accidental sequences or license the assertion of
counterfactuals.
It seems clear that if we are to get any further in
our search for the surplus-element the idea of purely
formal differentiae must be abandoned. Inductive
considerations prove no better than deductive ones. For
accidental generalizations may be inductively confirmed,
just as they may be deductively explained. In practice
then the non-radical empiricist, if he is not to concede
the game, is forced to re-examine the account of science
that seems to render any non-Humean conclusion
impossible. The fundamental fact about science that has
been missing from the discussion so far is the existence
at any moment of time of an antecedently established body
of theory. And it is here that the
11 J S. Mill, A System of Logic, Vol. I, p. 378.
152 A Realist Theory of Science
non-radical empiricist attempts to locate the
surplus-element. But can `theory' do what experience and
deducibility fail to do, i.e. provide a rational ground
for our ascriptions of natural necessity? The answer
clearly depends upon the extent to which the former
contains components irreducible to the latter. And the
onus is on the philosopher who attempts to locate the
surplus-element in the systematic organization of our
knowledge or the capacity of a theory to explain many
different laws12 or to predict novel kinds of facts13 to
show how their concept of theory escapes Humean analysis.
Goodman's notion of entrenchment,14 for example,
functions in exactly the same way as Hume's notion of
custom and can no more justify our attributions of
necessity than the latter could.
In short, unless theory contains elements
irreducible to experience and truth-functional operations
on it there is no basis for a non-Humean theory of
natural necessity.15 Thus the possibility of the latter
depends upon some terms of the theory not being
explicitly defined in terms of experience and/or some
statements of the theory not being deductively connected
and/or some ideas of the theory being non-propositional
in logical (or non-sentential in linguistic) form. These
establish the possibilities of intensional relationships
between predicates, non-deductive (e.g. analogical)
relationships between ideas and non-propositional
(e.g. iconic) ideas respectively as potential sources of
necessity. It is the second of these that has been most
thoroughly explored; and it is to Campbell's initial
formulation of the theory of models that I now turn.
On Campbell's view a theory must contain not only a
`dictionary' correlating some, but not all, of the
theoretical concepts with empirical terms but a `model'
for the hypotheses or theoretical statements of a theory,
by means of which its hypothetical subject matter may be
imagined to be like in some, but not all, respects the
real empirical subject matter of some field which is
already known.16 On this view the surplus-
12 E. Nagel, op. cit., pp. 64-5. 13 I. Lakatos,
op. cit., p. 116.
14 N. Goodman, op. cit., pp. 92-122.
15 For, as Craig's theorem shows, if it does not the
theoretical component is then completely eliminable. See
W. Craig, `The Replacement of Auxiliary Expressions',
Philosophical Review 65 (1956), pp. 35-55.
16 N. R. Campbell, The Foundations of Science,
esp. Chap. 6.
The Logic of Scientific Discovery 153
element just is the model. Thus what distinguishes
Boyle's law from a merely accidental generalization is,
according to Campbell, the corpuscularian model informing
the kinetic theory of gases. By means of this model gas
molecules are imagined to be, in certain respects, like
billiard balls bouncing off each other and exchanging
their momentum by impact. And it is in our prior
understanding of this that the necessity of the gas laws
ultimately lies. Notice that for Campbell it is not the
mere availability of a theory or even the organization
that the theory makes possible (e.g. the fact that
Boyle's law, Charles' law and Graham's law are all
deductive consequences of the kinetic theory) but the
interpretation theory explains.17
As a critique of the deductivist view of the
structure of scientific theories, as typified by Mill,
Duhem and Hempel, Campbell's case is a strong one. The
deductivist, he says, merely exhibits `the dry bones of
science from which all the spirit has departed".18 His
project is to revitalize it. He sees the driving force
of science as the exploitation of analogies in the
conquests of new fields, without which neither theory nor
the range of facts could grow or the language in which to
state them develop.19 But is his case unanswerable? How
does it fare when faced with the challenge of radical
empiricism? Is it capable of providing an adequate
account of the surplus-element in the analysis of
law-like statements? To answer these questions we must
look more closely at the terms of the modelling
relationship which is intended to provide the basis for a
non-Humean theory of natural necessity.
Now essential to Campbell's correction of the
deductivist view of explanation is the idea that for the
explanation of a range of phenomena say E_a to have
occurred the relationship between the theory T_a which
explains the phenomena and from which the latter is
deducible must be supplemented and informed by another
relationship. This is a relationship of analogy not
deduction; and it is by means of it that we render T_a
intelligible to ourselves. See Diagram 3.2 below.
According to Campbell the entities and processes
postulated at T_a are unknowable; i.e.
17 Ibid. pp. 126-40.
18 N. R. Campbell, What is Science?, p. 99.
19 N. R. Campbell, Foundations, pp. 132-7; and
M. B. Hesse, op. cit., pp. 35-43.
154 A Realist Theory of Science
they do not constitute part of the phenomenal world
described by science. Although we cannot know what
produces E_a we can imagine it to be like something we do
know. Such an act of imaginative daring need not be
totally arbitrary. For it is possible to conceive of
principles of analogical, just as there are principles of
deductive or inductive reasoning. Only when we have
constructed a model can we be said to have achieved
T_a
|\
| \
| \ Analogy
| \
| \_
Deduction V /\
| \
| \
E_a E_b
Diagram 3.2
Campbell's `Theory'
scientific understanding. That is, not just saved the
facts, preferably with elegance and economy, but
explained them. Using the analogy provided by E_b a real
or empirical phenomena can thus `enliven' the abstract
theoretical relationships from which E_a is deduced. And
E_b does this by standing in for or representing (in the
sense of the German `darstellung') the unknown causes of
E_a. Explanation thus involves, centrally, the
substitution in our imagination of a real or empirical
relationship for an unreal or theoretical one.20 This is
Campbell's debt to empiricist ontology: a debt that it
summed up by his tacit acceptance of the concept of the
empirical world. For on his theory T_a cannot be, or
come to be known as, real; though it is at any moment of
time, and perhaps forever, unperceivable to us. For him
theoretical entities, such as molecules, can only be said
to be `real' by analogy with material objects.
Campbell does not deny that deducibility is
necessary for explanation, merely that it is sufficient.
His theory may thus be regarded as providing an
alternative shave to Occam's razor. Tyndall formulated
the criterion for the selection of explanations
20 N. R. Campbell, op. cit., pp. 243-56.
The Logic of Scientific Discovery 155
implicit in Campbell's theory as follows: `ask yourself
whether your imagination will accept it'.21 Now such a
criterion is clearly capable of selecting a theory within
a given metaphysical schema, such as that provided by the
classical mechanical world-view. But it is not capable
of judging between different schemas, when it is
precisely the nature or the limits of the imagination
that is in question. To take an obvious example:
Aristotelian and Galilean dynamics are in conflict over
whether when a stone falls to the earth, the earth should
be conceived as fixed (Aristotle, Ptolemy and Tycho
Brahe) or as moving (Copernicus, Giordano Bruno, Kepler
and Galileo). Now, try as you may, there is no neutral
way of conceiving the falling of the stone.22 Our
imagination, although not fixed, is either Aristotelian
or Galilean. Tyndall's criterion cannot help us to
decide between the competing frameworks, because what it
in question is the nature of the concept in terms of
which any motion has to be understood.
There is a similar break involved in the transition
from Newtonian to Einsteinian dynamics. Part of the
trouble with current micro-physics is that our
imagination cannot accept it, and yet we have every
reason to believe it to be true. If Tyndall's criterion
were acted upon it could have effects on scientific
practice as conservative and dogmatic as the consistency
and meaning-invariance conditions of classical
empiricism. A new scientific ontology or a fundamental
change in scientific concepts may transform our
conception of what is plausible. At such times in the
history of science it becomes necessary for the scientist
to stand Tyndall's criterion on its head, and dizzily ask
himself whether he can continue to accept his imagination.
Although its inadequacy to deal with fundamental
scientific change is most evident, Tyndall's criterion is
no less inadequate to deal with the continuing processes
of conceptual micro-adjustment, in which our imagination
is continually modified and extended, that are a part and
parcel of the process of `normal science'. More
generally, it is always legitimate for
21 J. Tyndall, `Scientific Uses of Imagination',
Fragments of Science for Unscientific People, p. 131.
22 P. K. Feyerabend, `Problems of Empiricism, Part II',
The Nature and Function of Scientific Theory,
ed. R. G. Colodny, p. 317.
156 A Realist Theory of Science
scientists to ask and sometimes possible for them to
answer, questions about whether gases are really composed
of molecules or whether the earth really moves. Such
questions cannot be rephrased as questions about the
plausibility of our conceptions. This would be, in terms
of Diagram 3.1, to reduce phase (1) to phase (2). Rather
the normal procedure in science is if we have a plausible
conception to go on to ask whether it is true, which is
to ask whether the entities and processes it postulates
are real, or only fictional. Plausibility is a prima
facie criterion for a theoretical explanation. But is is
neither sufficient, nor in the last instance necessary.
How does Campbell's theory fare as a response to the
challenge of radical empiricism? According to it, the
surplus-element in the analysis of law-like statements is
the model at the heart of the theory that explains it.
But for Campbell the model cannot prompt questions about
the reality of the abstract entities and processes
postulated in the theory. For theoretical entities are
by definition unperceivable and hence, given the
fundamental equation of empiricist ontology, viz. real =
empirical, cannot exist. Models function then not as
knowledge-extending but as essentially pragmatic devices,
servicing the needs of the understanding. Theory
involves a journey from one set of experiences E_b to
another E_a. Because of this it is always possible for
the radical empiricist to ask whether the journey is
really necessary. Moreover, even if a way could be found
of showing that some model is necessary, there would seem
to be no way of justifying the choice of any particular
one (given that the idea that its necessity could be
demonstrated a priori is rejected as being inconsistent
with the fact of scientific change).
To this it may be contended that models are
necessary not only as conceptual crutches for the
tender-minded and as heuristic devices for the young
(which the radical empiricist may graciously concede) but
for a theory's growth and development, and in particular
(so as not to beg the issue by positing non-empiricist
criteria of development) for the generation of facts
empirically relevant for the theory but which would not
have been forthcoming without it.23 But this only pushes
the argument back a stage further. In a completed
science models would
23 See e.g. M. B. Hesse, op. cit., pp. 35ff. Cf. also
P. K. Feyerabend, `Problems of Empiricism', op. cit.,
pp. 173ff.
The Logic of Scientific Discovery 157
be dispensable. For, as Duhem has put it, `to explain is
to strip reality of the appearances in which it is
wrapped as in veils in order to see this reality naked
and face to face'.24 When we have done this, what more
can there be to do? The objection that `explanations
are practical context-bound affairs'25 either is covered
by the heuristic role allowed to models or depends upon
the incompleteness of science, in which case their
nemesis is merely (if perhaps indefinitely) postponed.
We are thus forced inexorably back to a particular
conception of reality, the only `world' that Campbell's
account of science contains: the world of Mach and Hume.
In such a world causality is bare and invariant
conjunction; and scientific knowledge consists, for its
part, in `description, that is the mimetic reproduction
of facts in thought, the object of which is to replace
and save the trouble of new experience'.26
Suppose now that arguments are advanced to show that
no science can ever be complete in the requisite sense.
Science still remains, on the Campbellian conception, a
purely internal process, locked in a dosed circle of
thought. Science is still a creature of custom and
habit, the only difference being that the habit is now
one of the imagination, rather than sensation. In virtue
of their shared ontology Campbell is closer to Mach and
Tyndall to Occam than one might think.27 In neither case
can the possibility of major conceptual revisions be
accommodated or the mechanism of scientific discovery be
displayed.
Let us apply to Campbell's theory the litmus test
for the adequacy of an account of science developed in
Chapter 1. Can it sustain the idea of the applicability
of the concept in question, viz. that of necessary
connection, in a world without men? The answer is
obvious. In the case of Campbell, as of Hume, there is
still no difference, independent of men, between a
necessary and an accidental sequence of events. The
Campbellian can at best talk of a nomically necessary
statement; he cannot talk of a nomically necessary
sequence. The attempt to locate
24 P. Duhem, op. cit., p. 7. 25 M. Scriven, `Truisms',
p. 450.
26 `This', says Mach, `is all that natural laws are',
op. cit., p. 192.
27 Indeed one might be tempted to see the difference as
merely one of taste or temperament as when Duhem compared
the `rolling drums', `pearl beads' and `toothed wheels'
of the mechanical models of English physicists such as
Maxwell, Kelvin and Lodge with his own Cartesian
conception of an axiomatic electricity. See op. cit.,
pp. 70-l .
158 A Realist Theory of Science
the surplus-element in the analysis of law-like
statements in the imagination of men is a failure.
For transcendental realism the surplus-element
distinguishing a law-like from a non law-like statement
is the concept of the generative mechanism at work
producing the effect in question. Such mechanisms exist
and act independently of men; so that the necessity can
be properly ascribed to the sequence. Moreover as the
world is open not all events will be connected by a
generative mechanism; so that the transcendental realist
can sustain a concept of natural accident.
Only a real difference between necessary and
accidental sequences can justify our distinguishing
law-like from non-law-like statements. Hence one cannot
deny Humean conclusion (b) (on page 149 above) without
objecting to Humean conclusion (a), and thus to the
ontology that implies it.
Nowhere is the anthropocentricity of post-Humean
philosophy more evident than in the notion that natural
necessity must be sought in the behaviour or nature of
men. And nowhere is the displacement of rational
intuitions more obvious than the attempt to locate
structure in the imagination of men. `Connection' is, as
Chisholm has remarked, an `ontological category and a
source of embarrassment to empiricism'.28 But it is not
an irreducible one. For its basis lies in the generative
mechanisms of nature which connect events as cause and
effect and which exist as the powers of things. Thus to
assert a counterfactual is not to make a meta-statement29
(which would be to make a statement about its grounds),
but to make a statement about the way some thing would
have behaved (exercised its tendencies, liabilities or
powers) had the conditions in fact been different.
Theory is not an elliptical way of referring to
experience,30 but a way of referring to hypothesized
inner structures of the world, which experience can (in
ways to be explored in paragrpah 3 below) confirm or falsify.
We are not locked in a dosed circle of thought; because
there are activities, viz. perception and
experimentations by means of which under conditions which
are deliberately generated and carefully controlled,
relatively independent cross-bearings on the intransitive
objects of thought
28 R Chisholm, op. cit., p. 496.
29 See e.g. E. Nagel, op. cit., p. 75; or S. Toulmin,
op. cit., p. 185.
30 Ibid., p. 185.
The Logic of Scientific Discovery 159
can be obtained. Such activities are not independent of
thought, but their results are not implied by them
either.
Campbell's achievement is to have seen that
scientific theory cannot be identified with a deductive
system erected on the basis of a single set of
experiences. But he made two mistakes. He too, like the
empiricists, missed the essential point that science is
essentially developing; so that the hypothetical
mechanisms of yesterday may become today's candidates for
reality and tomorrow's phenomena. But behind this
failure also lay an inadequate intransitive dimension,
and in particular the absence of the concept of objects
apart from our changing knowledge and possibilities of
perception of them. Campbell's theory has been extended
in two ways. Some have rectified his first mistake but
not his second, and viewed science as a sequence of
models, an unfolding process of shifts in intellectual
fashion. Others have developed his theory in a realist
way. Harre, for example, has drawn attention to the role
of the existential questions prompted by the creative use
of analogies in the development of science.31 By way of
concluding my discussion of Campbell's theory I want to
sketch out such a dynamized realist version of it.
In Diagram 3.3 below the dotted lines now stand for
relationships of deduction and the continuous lines for
relationships of
T_alpha
/|\ (vertical lines
/ | \ dotted, all others
/ | \ continuous)
/ | \
/ | \
/ | \
/ | \
/ | \
E_x / |E_alpha \E_ta = T_a
______________________________________________
| |\
| | \
| | \
| | \
| | \
| | \
| | \
| | \
| | \
E'_a <-- E_a E_b
Diagram 3.3
A Dynamic Realist Development of Campbell's Theory
31 R. Harre, op. Cit., esp. Chaps. 2-3.
160 A Realist Theory of Science
analogy (to indicate their reversed relative importance).
T_a has come to be established as real, and in this case
also is perceivable. In the course of this process facts
E_a have been corrected and now become facts E'_a. T_a
now provides one of the sources for a new model designed
to explain phenomena E_a. And the process of checking
its reality (which will almost certainly modify our
conception of it) has begun. Needless to say there will
in general be more than one model for E_a. The state of
chemistry c.1930 provides an illustration of the model.
T_a is Prout's hypothesis and T_alpha the theory of
sub-atomic structure. E_a-->E'_a, consists in the
elimination of the impurities that dogged the
verification of Prout's hypothesis for over a century.
And the new model might be the Bohr-Rutherford model of
atomic structure; which conceived as a hypothesis about
the internal structure of atoms is, we now know, false.
The source of such models may lie either in some general
conceptual scheme (such as atomism in chemistry) or some
other science or proto-science (such as the wave models
of light and sound in particle physics). The subject of
such models is the unknown but knowable intransitive
structure of the world. It is by means of the
experimental testing of the hypotheses suggested by
already existing knowledge that new knowledge comes to be
produced.
The problem of the surplus-element, and Hume's
challenge, has another aspect. This turns on the question
of what warrant we have for distinguishing between cases
of genuine and pseudofalsification, and hence for
invoking the CP clause in defence of generalizations in
the former case. This calls into question the necessity
of deducibility, not just its sufficiency in the
explanation of laws.
Science needs a concept of pseudo-falsification for
three reasons, two of which are epistemic and one of
which is ontological. Firstly, because a theory may not
be at present sufficiently refined or developed to cope
with anomalous counter-instances; that is to say, every
theory needs a `protective-belt' for its development.31
Secondly, because the `facts' may be wrong: either in the
simple sense that they are misrepresentations of the
phenomena or more profoundly because they depend upon
32 I. Lakatos, op. cit., pp. 134-8.
The Logic of Scientific Discovery 161
false or inadequate observational theories.33 As is well
known, every new theory is faced with innumerable
anomalies and counter-instances of these kinds. They
form in a sense the staple diet of normal science. A
successful theory is one which, like Newton's, though it
never resolves them all and generates new ones in the
process of their resolution, `turns each new difficulty
into a victory for its programme'.34 Thirdly, science
needs a concept of pseudo-falsification because a
countervailing cause or interfering agent may be at work
generating the `counter-instance'. It is only under
closed conditions, as we have seen, that a theory can be
given a fair test or that a crucial experiment - Bacon's
`instance of the fingerpost'35 - becomes possible.
The problems of the necessity and universality of
law are indeed inextricably linked, but not in the way
Hume thought. For if the surplus element in the analysis
of law-like statements is the concept of a generative
mechanism at work and this concept is irreducible to that
of a sequence of events then it is quite rational to
uphold an ontological distinction between cases of
genuine and pseudo-falsification (in which, as
exemplified by the case of Prout's hypothesis referred to
above, our epistemic distinctions too may be grounded).
For we may readily allow that the generative mechanism in
virtue of which natural necessity is ascribed is not
undermined by the instability of the conditions under
which it operates. So that if a law has been confirmed
under closed conditions and there is no reason to suppose
that the generative mechanism at work in those instances
has ceased to operate, the law that the concept of the
mechanism grounds may be supposed to continue to apply
outside the conditions under which it was confirmed,
whether or not the consequent of the statement happens to
be realized.
By now it would, I think, be generally agreed that
models play some cognitive role in science and that there
is a feature about such models which renders them
irreducible to the experiences that they are in some way
intended to embroider or explain. (This feature is, I
have argued, typically an idea of a
33 As Feyerabend has put it: a theory may be in trouble
only because of `the backwardness of the observational
ideology'. See `Problems of Empiricism, Part II',
pp. 292ff.
34 P. S. de Laplace, The System of the World, Bk. III,
Chap. II.
35 F. Bacon, op. cit., Bk. II, Aphorism XXXVI.
162 A Realist Theory of Science
mechanism which would, if it were real, generate the
phenomena in question.) But the representatives of the
three traditions in the philosophy of science differ
radically in their interpretations of the status and role
of such models, and of the irreducible concept that
constitutes its essential core.
The classical positivist view is that it is merely a
heuristic device (Duhem, Hempel and Brodbeck). This is
liable to encourage the view that the rationale for
distinguishing necessary from accidental sequences is
solely pragmatic; that it is, as it were, a question of
our greater attachment to the former (Quine),36 or of the
deeper entrenchment of their predicates in our conceptual
system (Goodman). Similarly it encourages the idea of
the CP clause as a device that can be relaxed or invoked,
switched off or on, according to whether or not we are
prepared to forego the falsified law-like statement.
This view carries the implication of course that the use
of the CP clause is bound to be more or less arbitrary or
dogmatic.37 And this in turn creates the Kuhn-Popper
problem of the functions of dogma.
The concept of the generative mechanism may be given
a firmer status, and the distinctions it grounds a better
rationale, by seeing its function as concerned
essentially with the development of science. Protection
from pseudo-falsification then becomes protection from
too easy or too early falsification; that is, before the
full potentialities of the theory have been developed
(Lakatos and Feyerabend). This view allows that our
knowledge is structured - that it contains, as it were,
layers of different age. The conditions of knowing are
here explicitly distinguished from the conditions of
being. But positivism still provides the underlying
account of the world. And because of this the rationale
of the concept of the generative mechanism, which forms
the heart or essential core of the theory, is still more
or less pragmatic, still science- or knowledge- or
man-dependent.
The third position consists in coming to see not
just our
36 `Any statement may be held true come what may, if we
make drastic enough changes elsewhere in the system',
W. V. O. Quine, From a Logical Point of View, p. 43.
37 See e.g. K. R. Popper, Logic of Scientific Discovery,
p. 42 and pp. 80-2; and T. W. Hutchison, The
Significance and Basic Postulates of Economic Theory,
pp. 40-6. I have of course argued (in 2.4 above) on
quite distinct realist grounds that once the
irrationality of pseudo-falsification is granted the CP
clause becomes superfluous.
The Logic of Scientific Discovery 163
knowledge but the world itself as structured and
differentiated. According to this conception, which is
that of transcendental realism, science is concerned
neither with the incessant accumulation of confirming
facts (or the incessant search for falsifying ones), nor
even with its own growth and development, but rather with
the understanding of the different mechanisms of the
production of phenomena in nature. Thus it allows that
under certain conditions the concept of the generative
mechanism at work may be given a realist interpretation
as a representation in thought of the transfactually
active causal structures of the world. The possibility
of such an interpretation supplements internal
consistency and contextual plausibility as a constraint
on the possible forms of theoretical advance; and it
constitutes the ultimate goal of all theory construction.
Now empirical realism generates the following
dilemma: Either theoretical entities refer ultimately to
experience, in which case they can be eliminated. Or
theoretical entities constitute experience (in whole or
in part), in which case they cannot be eliminated, but
must, given the equation of empirical realism, constitute
the world (in whole or in part). Now as long as an
ontology based on the category of experience is retained
there can be no grounds independent of man for ascribing
necessity to some but not other statements. On the first
horn this generates the problem of what justifies our
belief that the future will resemble the past, or the
unobserved the observed, i.e. the problem of the
induction. But on the second horn it generates the
problem of what justifies the assumption of intellectual
conformity. And, on this horn, scientific change, or
even dissent, actually constitutes (in whole or in part)
a breakdown in the uniformity of nature!
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