CHAPTER 7
REALISM
INTRODUCTION
So, you’ve discovered your hypothesis and you’ve subjected it to rig-
orous testing, taking into account all that we’ve said so far, and it
seems to be holding up in the face of all the evidence. Does that
mean that what it says about the world is true? Does that mean that
the objects and processes it presents to us actually exist? The obvious
answer would be to say, ‘yes, of course’ and if you are inclined to
adopt that line, then you are a ‘realist’ of some stripe or other. Now
it might seem the most obvious answer but, as we’ll see, objections
can be raised to it. Those who raise such objections are known as
‘anti-realists’, and again as we’ll see shortly, they too come in
different forms.
So, this is the fundamental question for this chapter: What do
scientific theories tell us? Here are three different answers:
Aji They tell us how the world is, in both its observable and unob-
servable aspects (realism).
This is the realist answer. Realists take theories to be true, more or
less, and tell us how the world is, not just with respect to what we can
observe, but also when it comes to unobservable features as well.
Now, drawing the distinction between the observable and the unob-
servable is a bit tricky. First of all, do we mean ‘observable’ with the
naked eye, or with scientific instruments? Scientists themselves
adopt the latter understanding and talk of observing biological
processes, molecules, even atoms. But then even if you’re happy with
talk of observing microscopic bugs through an optical microscope,
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REALISM
I’m willing to bet you’re less comfortable about observing clusters of
atoms though a scanning electron microscope. In the former case we
have a set of intervening lenses between our eyes and the sample; in
the latter, we have a much more complex set-up of electrical devices,
not to mention the computer enhancement involved. Now you
might say that it shouldn’t matter how the observing instrument is
constructed and that we simply can’t draw a sharp line between those
devices which contribute to ‘genuine’ observations and those which
do not. If you say that, you might be inclined to go one of two ways:
either it doesn’t matter whether you use instruments for observation;
or it does, and naked-eye observation is the only form that counts.
Even if you adopt a hard line and go with the latter option, things
are still not straightforward. On the one hand, it seems that we can
come up with some clear-cut cases: the green mould in the Petri dish
is observable; sub-atomic particles are not. On the other hand, there
are equally obviously grey areas: very large molecules or bugs on the
borderline of microscopic, for example. Now this is not a problem
for the realist. If her theory is appropriately justified and she takes it
to be true, then no matter how we characterise the distinction
between observable and unobservable, she will accept the objects put
forward by the theory as ‘out there’ in the world. The anti-realist, of
course, will adopt a different view.
Here’s a different answer:
A2: Theories tell us how the world is, in its observable aspect only
(instrumentalism).
Realism has its problems as we will see. In particular, unobservable
entities have come and gone throughout history. So one option is to
draw the above line and insist that the worth of theories lies not in
whether they are true or false but simply in how useful they are when
it comes to explaining and predicting phenomena. In other words,
rather than telling us how the world is, theories should be regarded
as nothing but instruments themselves, that we use for predicting
more observable phenomena (hence the name, ‘instrumentalism’).
This is a view that has fallen out of favour in recent years, mainly
because theories function in scientific practice as more than mere
instruments for prediction. That’s why the most well-known form of
modern anti-realism adopts the following answer to our original
question:
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SCIENCE: KEY CONCEPTS IN PHILOSOPHY
A3: Theories tell us how the world is, in its observable aspect and
how the world could be, in its unobservable aspect (constructive
empiricism).
This view accepts that theories play a role in science that goes
beyond acting as simply prediction machines. However, for the sorts
of reasons we shall look at below, it retains doubts about unobserv-
able entities and processes and insists that whereas theories tell us
how the world is when it conies to the observable features, we simply
cannot be sure that they tell us how things are when it comes to the
unobservable, only how the world might be. Let us explore these
positions in more detail.
SCIENTIFIC REALISM
As we have just indicated, according to the ‘realist’, scientific theories
correctly describe the way the world is; that is, scientific theories:
• are true
• correctly describe what kinds of things there are in the world
(observable and unobservable)
• correctly describe the ways in which these things are related
Now this seems a straightforward position but even at this stage in
the proceedings we need to exercise a little care. First of all, by ‘truth’
here the realist means truth in the standard, no muss no fuss corres-
pondence sense; that is, a statement is taken to be true if it corres-
ponds to a state of affairs in the world. But this might seem too
strong because we know from the history of science that theories
come and go, that even those that are taken to be true at one time
come to be abandoned and replaced at another. The obvious
response for the realist to take is to acknowledge that earlier theories
were not completely true but only approximately so, and that subse-
quent theories are improving on that approximation and taking us
closer and closer to the truth. That seems a plausible picture but it
turns out that filling in the details is more difficult than it might
appear. There are other, more acute problems that the realist has to
face, however, as we’ll see.
Secondly, we surely should not take all theories or hypotheses to
describe the way the world is. What about speculative hypotheses,
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REALISM
hypotheses that have passed a few tests but about which we still have
doubts? That’s a fair question and typically the realist restricts her
realist attitude to mature theories; that is, those theories which:
• have been around for a while (that is, they’re not speculative or
cutting-edge)
• are generally accepted by the scientific community (there is a
general consensus that they’re on the right track)
• are seriously tested (they have survived falsification)
• are supported by significant body of evidence (they have been
verified).
These are the theories that tell us how the world is, at least as far as
the realist is concerned.
Now this might all sound plausible, but can we give an argument
for realism? You might think that a good argument is that many sci-
entists are realists; indeed, such an attitude might seem to be a pre-
requisite for doing scientific research. After all, how can you
investigate something if you don’t think there’s anything there to
begin with? Well, first of all, not all scientists are realists. Many of
the heroes of the quantum revolution, for example, concluded
that it simply wasn’t possible to give a realist interpretation of the
new theory and retreated to a form of instrumentalism. Further-
more, even if adopting a realist attitude is necessary to do research
(and its not completely clear that it is; after all, I can believe that
something is out there without accepting that the various aspects of
my theory correspond to it), we could say that this is just a matter
of psychology, of getting into the right frame of mind, rather than
the basis of a convincing argument. Why should we, as philoso-
phers of science attempting to understand scientific practice, adopt
a realist attitude simply because scientists have to in order to do
their work? Is there a better argument we can give? Indeed there is.
THE ‘ULTIMATE’ ARGUMENT FOR REALISM (AKATHE ‘NO
MIRACLES ARGUMENT’)
This is the argument that is most often given in order to try to con-
vince someone to be a realist about scientific theories. It is nicely
and famously summed up by the philosopher Hilary (not a girl)
Putnam, as follows: ‘The positive argument for realism is that it is
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SCIENCE: KEY CONCEPTS IN PHILOSOPHY
the only philosophy that doesn’t make the success of science a
miracle.’57 The central idea here is that realism is the best (perhaps
even the only) explanation of the success of science. The main
reason we’re looking at scientific practice in the first place is because
science is so massively successful: it has changed our world through
its technological implications, giving us antibiotics, genetic mani-
pulation, supercomputers and iPods, and it has changed our
fundamental picture of the world, giving us evolution, curved
space-time and quantum entanglement. More particularly, scienti-
fic theories are spectacularly successful in terms of making predic-
tions that then turn out to be correct. How can we explain this? It’s
either an amazing (and repeated) miracle, or these theories have,
somehow, got it right. Given our reluctance to accept miracles in
this secular age – and this goes way beyond the odd burning bush –
it would seem that the only conclusion we can draw is that the best
explanation for the success of science is that our theories are true
and tell us how the world is.
Furthermore, the realist might point out that this form of argu-
ment is no different from that used by scientists themselves with
regard to their theories: just as scientists select a particular theory on
the grounds that it’s the best explanation of a phenomenon, so the
realist argues that her philosophical view is the best explanation of
the more general phenomenon of the success of science. So there’s
nothing odd or philosophically tricky about this argument – it’s just
the same kind of argument that scientists use. This forms part of a
general view known as ‘naturalism’ which takes philosophy and
science to form a seamless whole and that philosophers should use
the same sort of argumentative strategies.
So, the realists’ ultimate argument for the truth of scientific
realism is basically the same argument for the truth of scientific the-
ories; that is,
• scientists argue that theory T is best explanation of phenomena
/. T is true
• realists argue that realism is the best explanation of the success of
science
/. realism is true.
Now, we’ll come back to this ‘No Miracles Argument’ shortly, but
let’s examine some of the problems this realist package faces.
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REALISM
PROBLEM 1: THE PESSIMISTIC META-INDUCTION
The realist holds that our best, mature theories are true, or at least
close to the truth. Enter the historian of science who laughs (evilly)
and says ‘been there, done that’ and reminds us of all the theories
through history that have been empirically successful but in fact sub-
sequently shown to be false, in the sense that they don’t correctly
describe what kinds of things there are in the world and/or don’t cor-
rectly describe the ways in which these things are related. And if that
was the case in the past, how can we be sure that our present, empir-
ically successful theories won’t also subsequently be shown to
be false? And if that is the case, how can we be realists about these
theories?
This argument against realism is known as the ‘pessimistic meta-
induction’: it’s a kind of inductive argument which uses examples
from the history of science, rather than from science itself; so it’s called
a ‘meta-induction’ because it works at the level above that of science
itself (the ‘meta’-level); and it’s pessimistic because it concludes that
we can’t regard our current theories as true and hence can’t be realists.
And it seems quite a powerful argument. What examples are typically
given of past theories that were successful at the empirical level but we
now agree are false? Here’s a list of well-known examples:
the crystalline spheres of Greek (Aristotelian) astronomy
the humours of medieval medicine
the effluvia of early theories of static electricity
catastrophist geology
phlogiston
caloric
vital force (physiology)
the electromagnetic ether
the optical ether
circular inertia
spontaneous generation.
Other theories can be found but these are some of the more well
known. So, here’s the argument again:
The history of science presents us with examples of successful theo-
ries that are now recognised as false; therefore our current successful
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SCIENCE: KEY CONCEPTS IN PHILOSOPHY
theories are likely to turn out false; therefore we have no grounds for
adopting a realist attitude towards them.
Now how can the realist respond to this argument? Well, she can
point out that some of these examples were not particularly well
developed, like the crystalline spheres or the humoral theory of med-
icine; that is, she can tighten up on the maturity constraint. In par-
ticular, she can insist that for a theory to be regarded as really
mature, to be really worthy of a realist attitude, it should make novel
predictions’, that is, predictions about phenomena that were not con-
sidered in the discovery or development of the theory in the first
place. Recycling our iconic example once again, the prediction that
starlight would follow the curvature of space-time and be bent
around the sun did not feature in the heuristic moves that lay behind,
or in the subsequent development of, Einstein’s General Theory of
Relativity.
This extra criterion rules out some of the above examples – the
crystalline spheres made no such predictions; nor did the humoral
theory of medicine – but not all. Consider the caloric theory of heat,
for example. This is the apparently plausible theory that heat is a
kind of substance, called ‘caloric’, which flows like a liquid from a
hot body to a colder one, and hence explains why hot and cold
bodies brought into contact tend to reach the same temperature.
This was an empirically successful theory that explained the expan-
sion of air when heated (as caloric is absorbed by the air molecules)
and also made novel predictions, to do with the speed of sound in
air. But we now accept that the theory is false, and that heat is really
the motion of molecules. So, if we had adopted a realist attitude
towards the caloric theory we would have been caught out; it satisfies
all the realist criteria but it was subsequently shown to be false. And
if that could happen to the caloric theory, it could happen to our
current well-regarded and accepted theories. Hence we should not
adopt a realist attitude towards them.
PROBLEM 2: THE UNDERDETERMINATION OF THEORY BY EVIDENCE
Which theories should we be realists about? Well, as we said, the
ones that are empirically successful make novel predictions and are
generally ‘mature’. But what if we have two theories that are both
equally empirically successful? Which one do we then take to be
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REALISM
true? Consider two different theories about the extinction of the
dinosaurs. Theory 1 suggests that it was due to a massive meteor
strike that threw up huge quantities of dust into the atmosphere,
blocking the sun, changing the climate and destroying ecosystems.
Theory 2 posits that, on the contrary, it was due to massive volcanic
activity that threw up huge amounts of dust into the atmosphere,
blocking the sun, etc., etc. Which one is true? The obvious response
the realist can adopt would be to say that neither should be taken as
true, both should be regarded as provisional hypotheses and we
should withhold judgment until further evidence is obtained. So,
when we discover evidence of a huge meteoric impact crater off the
coast of Mexico, we can take that as further support for Theory 1.
But what if further evidence is found supporting Theory 2? What
if we discover evidence of enormous lava flows in India, indicating
dramatic volcanic activity around the time of the extinction? What
if whatever evidence we find to support a given theory, we can find
evidence supporting its competitors? The possibility of this is what
is known as the ‘underdetermination’ of theory by the evidence;
which theory we should accept as true is not determined by the evi-
dence. And it forms the basis of another argument against adopting
a realist attitude.
The central idea is as follows: for any theory T which is empiri-
cally successful and explains the phenomena, it is possible there
could be an alternative theory T’ which is just as empirically suc-
cessful and explains the same phenomena but puts forward a
different set of entities or presents a different way the world is. Now,
how strong an argument the realist takes this to be depends on just
how seriously she takes this as a possibility. Are there good cases of
underdetermination in science? We’ve just seen how the underdeter-
mination can be broken by new evidence that we discover. The realist
might suggest that this will always be the case. But suppose the anti-
realist is right: for whatever evidence we find for T, we can find
further evidence supporting T’. Perhaps the realist can break the
underdetermination by appealing to other factors.
For example, she might insist that we should believe whichever
is the better explanation of the phenomena. This then raises the
obvious question: What would count as a ‘better’ explanation?
Remember: both theories are equally empirically successful, so in
that sense they both account for the phenomena. There have been
many long discussions in the philosophy of science of what it means
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SCIENCE: KEY CONCEPTS IN PHILOSOPHY
to ‘account’ for the phenomena. Let’s digress a little to consider this
issue in more detail.
According to a well-known view that was held for many years, to
explain a phenomenon is to logically deduce a statement describing
it from one or more laws, plus the relevant conditions describing the
situation in which the phenomenon is observed. Take rainbows, for
example: we begin with the laws of optics, in particular the laws of
refraction and reflection, add the condition that the observer has to
be standing in front of the drops of rain, with the sun behind her,
and we deduce from the laws and the particular conditions a state-
ment describing a rainbow. Obviously it’s a bit more complicated
than that, but this gives the general idea. This view came to be
known as the ‘Deductive-Nomological’ or ‘D-N’ account of explan-
ation; ‘deductive’ because it’s based on the core idea that to explain
something, we deduce a statement referring to it from other, more
general, statements (in this case, scientific laws); and ‘nomological’,
from the Greek ‘nomos’, for law.
Now this appears to be a good account of what an explanation is,
and it held sway for quite a while. But it faces a number of objec-
tions. In particular, consider another example: it’s a sunny day and
a flagpole casts its shadow across the grass. On the above view, we
explain the length of the shadow by deducing it from, again, the laws
of optics and the height of the pole, together with the relative posi-
tion of the sun. No problem. But we can also go the other way:
knowing the length of the shadow, we can deduce the height of the
pole, using the laws of optics and knowing the relative position of
the sun. However, it would seem bizarre to claim that we had
explained the height of the flagpole in this way.
So, the D-N account seems to leave something out. What could
that be? Well, the reason we don’t think the length of the shadow
plus the laws of optics adequately explain the height of the flagpole
is surely because we know that its height is actually explained by
other factors, having to do with the length of wood that was cut and,
ultimately, the desires of the people responsible for erecting it. And
what this actual explanation gives us are the causal factors respon-
sible for the flagpole being the height it is. Similar factors can also be
cited to explain the length of the shadow: it is the combination of
the height of the pole and the position of the sun which causes the
length of the shadow to be what it is. So what the D-N account leaves
out are the relevant causal factors in an explanation.
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REALISM
Following this and other criticisms, the D-N view of explanation
seems to have been largely abandoned.58 These days there are a
number of competing accounts, including some that emphasise the
role of models in explanation, as we noted in the previous chapter.
Such an account might insist that a phenomenon is explained if it
can be appropriately represented through some model or other. Of
course, that takes the issues back a step, to an adequate account of
representation.
Rather than go into detail here, let’s accept that explanation has
something to do with the relationship between a theory and the phe-
nomena to be explained (and even that has been disputed).59 In cases
of underdetermination, both theories enjoy such a relationship. Is
there anything more to explanation that might help the realist select
one theory over another? Well, one explanation might be more
unified or more coherent than the other. So, the explanation of
extinction events that cites volcanic action might require there to be
more than one instance of such action having taken place, which
might just seem less plausible than one big meteor strike. Now, the
anti-realist can reply that appealing to plausibility seems pretty
weak, when we’re supposed to be dealing with the truth, at least
according to the realist. Perhaps it just was an unfortunate series of
volcanic coincidences that led to the demise of the dinosaurs (and
indeed, there seems to be a growing acceptance that the extinction
of the dinosaurs can be explained by a combination of both volcanic
action and a meteor strike).
But the realist can then counter by appealing to still other factors.
Perhaps one theory is just simpler than the other and should be pre-
ferred on those grounds, since it offers a simpler and hence better
explanation. Of course, the realist then owes us an account of what
simplicity amounts to – after all, Einstein’s General Theory of
Relativity doesn’t seem that simple to most of us! But, it would seem
that the realist can at least sketch out the basis of such an account:
perhaps she might say that a theory which posits fewer unobservable
entities in the world than another is simpler and to be preferred, so
a theory which explains electrical phenomena in terms of one kind
of charged object (negatively charged electrons) and their absence
(positive), rather than two differently charged fluids, say (as in
Benjamin Franklin’s theory), is better.
However, the anti-realist can ask an apparently devastating ques-
tion which sidesteps the whole debate about what we mean by
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‘simple’: what has simplicity to do with truth? Or, to put the point
another way, why should the simpler theory be closer to the truth?
Unless the realist can link simplicity and truth in some way, trying
to break the underdetermination by appealing to simplicity as a
factor isn’t going to help the realist’s case. Now, the realist might just
insist, as Einstein did, that the universe just is simple, but insistence
doesn’t amount to an argument and such claims start to look like
mere expressions of faith. After all, the universe could just be horri-
bly complex, even at its most fundamental level, and it might turn
out, then, that a very complicated theory is in fact closer to the truth.
What the realist needs is to show that truth tracks simplicity in some
way, and so far, she hasn’t been able to do that.
All is not lost, however. The realist has another card up her sleeve:
she might say, look, this is all a bit too crude and in actual scientific
practice, we don’t just consider the relationship between a theory
and the evidence when we decide whether to accept it or not. We also
consider other factors, such as the theory’s coherence with other,
already well-accepted theories, or with our background beliefs in
general. So, consider our dinosaur example again. The theory that
explains the extinction in terms of volcanic action gains extra
support from the more general theory of continental drift. This
explains a wide range of geological phenomena as due to the move-
ment of huge ‘tectonic plates’ on which the continents sit. Where two
such plates are moving apart, molten rock wells up from beneath the
earth’s crust, and it was observed evidence that this was happening
in the middle of the Atlantic which provided conclusive support for
the theory. Where these plates collide, one is forced underneath the
other and the region where this happens suffers from earthquakes
and volcanoes. So, the presence of major volcanic action at the time
of the extinction of the dinosaurs can itself be explained and made
sense of in terms of the theory of tectonic movements, and evidence
that there was such movement where and when the volcanic action
occurred can be regarded as indirect evidence for this explanation of
the extinction. That might provide a further reason for preferring
this hypothesis. In other words, establishing a relationship between
this hypothesis and a broader set of background geological beliefs
may help to break the underdetermination.
However, things are not that straightforward. The hypothesis of
a devastating meteor strike also gains support from our recently
acquired knowledge that such large interplanetary objects fre-
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REALISM
quently pass close (in astronomical terms) to the Earth. Indeed, it
has been noted that dramatic extinction events appear to have
taken place every 26 million years and it has been suggested that
this is the period of time over which the Earth encounters the ‘Oort
cloud’, a large ‘cloud’ of rocks and debris left over from the for-
mation of the solar system and from which asteroids and meteors
periodically emerge. Here we see astronomical background know-
ledge being appealed to in order to favour the meteor-strike
hypothesis. The problem is, as we now see, the adherents of each
theory can appeal to different kinds of background knowledge in
order to defend their claims and it may not yet be clear which set
carries more weight.
Of course, the realist might pin her hopes on some further
strengthening of the relationship between one of the underdeter-
mined hypotheses and the relevant background knowledge and
appeal to that in order to break the underdetermination. But there
is a straightforward response the anti-realist can make that appears
to undermine the whole project: she can simply ask ‘Why should we
take the relevant background knowledge to be true?’ Perhaps it too
suffers from underdetermination with respect to the given body of
evidence, so that some way had to be found to break that underde-
termination too. But then if that involved further background
knowledge – back-background knowledge – then the problem has
just been pushed back a step. This is what the philosopher calls a
regress and it’s not clear where it stops.
We need to leave it there for the moment but at least we can see
how this debate starts to open out into a whole range of other issues,
to do with the relationship between theory and evidence, the role of
factors such as simplicity, and the impact of background knowledge
on theory acceptance.
There is a final problem the realist must face, which goes to the
heart of the motivations for this view.
PROBLEM 3: THE ULTIMATE ARGUMENT BEGS THE QUESTION
We recall the ‘ultimate’ argument the realist gave for her position.
This was that realism offers the best explanation for the phenome-
nal success of science – how else is that success to be accounted for,
unless our theories are true, or more generally, have somehow got the
world ‘right’? And the realist insists that her argument for realism
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has the same form as the argument scientists themselves use for
accepting one theory over another, namely that that theory offers the
best explanation of the phenomenon. In other words, what the
realist is doing is nothing tricky, philosophically speaking, but
merely appealing to the same kind of argument – inference to the
best explanation – that scientists use themselves.
But now the question arises: Do scientists actually use this form
of argument? That is, do they conclude that a theory which is the
best explanation of the phenomena is true and should be accepted
as such? The answer is that some do, some don’t, and in claiming
that this is how all scientists operate, the realist is guilty of assum-
ing the very realist account of scientific practice that she is trying to
defend. This nefarious practice is what philosophers call ‘begging
the question’: you assume as part of your argument the very thing
that you are trying to argue for! Clearly that’s not going to stand up
as a compelling argument, particularly if you’re an anti-realist to
begin with.
But then the anti-realist might legitimately be asked for her
account of the success of science. In the next chapter we will
examine the most well-known current form of anti-realism, but let’s
just note here what form that explanation will take. Basically the
anti-realist insists that we need to be careful in asserting that science
is so tremendously successful. Clearly some theories and technolog-
ical spin-offs have been successful but to focus on this is to ignore
all the many other theories that were not so successful and which
fell by the wayside. The success of current science only looks so
impressive if we highlight the winners, and it appears less so if we
bring all the losers into the picture, and of course, out of the vast
array of theories put forward in the scientific journals and at con-
ferences every year, only a very few will survive the wolves of experi-
ence; most will be falsified or shown to be incoherent. The
anti-realist can make a nice comparison with the theory of evolu-
tion here: we notice that certain species appear to be fantastically
successful in their particular ecological niches – the polar bear for
example. One explanation is that there has to be something special
about that species, that it was designed to be that way. Darwin
offered a very different account in terms of ‘natural selection’
that eliminated the need for a designer – the species appears suc-
cessful because its competitors were not ‘fit’ enough. Likewise,
successful theories possess no special quality in terms of being true
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REALISM
or whatever, they are simply the ones that are ‘fitter’ than their
rivals, which could not survive scientific practice, red in tooth and
claw! (But can you see where the metaphor cracks under the strain?
We’ll come back to this in the next chapter.)
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CHAPTER 8
ANTI-REALISM
INTRODUCTION
In Chapter 7, we looked closely at the realist view of science. This
takes the aim of science to be truth, not in some funny, post-modern
sense, but in the sense of corresponding to states of affairs that are
‘out there’, in the world. And the main, some say ‘ultimate’, argu-
ment for this view is that realism is the only position that doesn’t
make the success of science a miracle. This is the ‘No Miracles
Argument’, or NMA. In other words, just as theories are accepted –
the realist claims – because they are the best explanations of the
phenomena they are concerned with, so realism is the best (indeed
the only) explanation of the success of science.
We then looked at the problems this position faces. First of all, the
historically minded will say ‘Been there, done that, and didn’t like
this view in the first place,’ pointing out that throughout the history
of science apparently successful theories have come and gone; theo-
ries that, had the realist been around at the time, she would have
accepted as the truth, or close to it, but since they were subsequently
thrown away as false, why should we believe that our current theo-
ries, amazingly successful as they are, should be regarded as true, or
approximately so? This is known as the ‘Pessimistic Meta-Induction’
problem, or PMI.
Secondly, the situation may arise in which we have two theories
that, it is claimed, are equally well supported by the evidence. This
is the Underdetermination of Theory by Evidence problem, or
UTE. If empirical success is supposed to be indicative of truth, how
is the realist going to decide which theory is true, or closer to the
truth? Now, the realist could always pin her hopes on further
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ANTI-REALISM
evidence coming in that will break the deadlock. But suppose that
never happens? What could she appeal to then? She might suggest
we go with the theory that is simplest, but then it’s legitimate to ask
what simplicity has to do with the truth. Or she could point to the
way one of the theories is better integrated with our background
knowledge than the other, but the same concern arises with regard
to the background knowledge and so the problem is just pushed
back a step.
And finally, there’s the criticism that the NMA begs the very ques-
tion at issue; that is, it assumes the very realist view it is designed to
support. If you’re not a realist, you’re not going to accept the claim
that scientists choose that theory which is the best explanation as
true and so you’re not going to be persuaded by the similar claim
that realism is the best explanation of the success of science. Of
course, the onus is now on you to come up with an alternative
explanation of that success, but as we saw, that’s not so difficult.
So, here’s this chapter’s fundamental question: How should we
respond to these problems? There are various answers to this ques-
tion out there in the literature but here I’m going to focus on just
three, well-known and, I hope, interesting alternatives.
ALTERNATIVE 1: CONSTRUCTIVE EMPIRICISM
This is perhaps the dominant form of anti-realism around in the
philosophy of science today. Basically, it identifies the source of the
PMI and UTE problems as being the appeal to unobservable enti-
ties and processes and urges us to restrict our belief to observable
things only. Now, it’s important to be clear how this form of anti-
realism differs from earlier forms, such as ‘instrumentalism’. The
instrumentalist, as the name suggests, took theories to be nothing
but instruments for the prediction of empirical phenomena and as
such, could not be regarded as true, or even approximately so.
Theoretical statements – that is, statements about unobservable
things like electrons, genes, the ego or whatever – are nothing but
shorthand summaries of whole lists of observation statements. So,
when a scientist states ‘DNA is composed of a series of nitrogenous
bases inter-connected by sugar and phosphate strands,’ the instru-
mentalist takes this to mean ‘When you do such an such an experi-
ment, you will observe such and such a result.’ (Obviously the list of
observations in each case will be huge!)
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The problem with this view is that it doesn’t mesh with scientific
practice. When a scientist says ‘All the evidence is in and it looks as if
our theory is pretty close to the truth,’ the instrumentalist has to
translate that as All the evidence is in and it looks as if our theory is
a pretty good prediction device.’ And when scientists talk about elec-
trons, genes, the ego, whatever, the instrumentalist has to say Ah,
what you’re actually talking about are mammoth lists of observa-
tions’ (to which the scientists might well respond ‘No, what we’re
talking about are electrons, genes, the ego or whatever’!). On this
view, we can’t take the language of science literally and we have to
translate all the talk and beliefs of scientists in terms of observations.
The constructive empiricist, on the other hand, takes the language
of science literally. She agrees that when scientists talk about unob-
servable entities, their talk is, indeed, about these entities and is not
mere shorthand for long lists of observation statements. And she
also agrees that theories are the kinds of things that can be true.
However – and here’s the twist – the constructive empiricist adds
what she takes to be a healthy dose of scepticism to the pot. How do
we know that theories are true, she asks? In particular, how do we
know that theoretical statements refer to the unobservable entities
they purport to? If we buy into the empiricist premise that all know-
ledge is only of the empirical, that is, the observable, that is, what we
can observe with the naked eye, then we clearly cannot know whether
electrons, genes or the ego exist, nor can we know, therefore, whether
theories are true or not. They might be, we just can’t know.
On this view, then, we shouldn’t believe theories to be true, or
approximately so. What attitude should we take towards them? Well,
what scientists do, as we have seen, is test their theories, seek empir-
ical support for them, try to determine whether they are adequate in
terms of accommodating the relevant observations. So, rather than
believe theories as true, we should simply accept them as empirically
adequate. As far as the constructive empiricist is concerned, this is
the appropriate attitude we should adopt towards theories and, fur-
thermore, we should drop the realist view that science aims at the
truth and acknowledge that its aim is empirical adequacy. Here’s
what the ‘founder’ of constructive empiricism says:
Science aims to give us theories which are empirically adequate;
and acceptance of a theory involves as belief only that it is empir-
ically adequate. . . . a theory is empirically adequate exactly if
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ANTI-REALISM
what it says about the observable things and events in this world
are true – exactly if it ‘saves the phenomena’.60
What do theories tell us, then? On the realist view, theories tell us
how the world is. But according to the constructive empiricist, we
can never know how the world is, since we can never know its unob-
servable aspects. On this view, theories tell us how the world could
be; that is, they provide us with useful stories of what the world
might be like, but we can never know if these stories are actually true
or not.
Now, you might find this a beguiling position; or you might think
it’s clearly mad! Before we make any critical judgments, let’s see how
it handles the three problems above.
So, first of all, how does constructive empiricism overcome the
PMI problem? We recall that at the core of PMI lies the claim that
the history of science presents us with case after case of radical
change at the level of unobservable entities. Phlogiston, caloric, the
ether have all been proposed by the respective theories and these the-
ories have even enjoyed some empirical success, but they were all
abandoned and these entities dismissed as unreal. Nevertheless,
there is steady cumulative growth through the years at the level of
the observable consequences of our theories. Of course, sometimes
what initially appear to be good experiments are discovered to be
flawed or problematic, but leaving these cases aside, the history of
science does seem to present us with an accumulation of empirical
results. (Some philosophers and sociologists have disputed this but
we’ll come to that in the next chapter.)
Now, it would seem that constructive empiricism can easily
accommodate this. If we think of a theory as merely telling us how
the world could be, then we shouldn’t be surprised, or at all both-
ered, when the evidence tells us that no, it couldn’t be like that. Of
course, that doesn’t provide conclusive evidence that the world is
how the next theory proposes it is; again, this is just another way it
could be. So the radical changes at the level of unobservables are
nothing more than changes of story, from The world could be like
this . . .’ to “Or it could be like that . . .’. In every case, we can’t
know for sure. And as the level of evidence accumulates, each suc-
cessive theory can be viewed as more empirically adequate than its
predecessor and so the growth of empirical knowledge can be
accommodated.
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SCIENCE: KEY CONCEPTS IN PHILOSOPHY
Secondly, how does constructive empiricism overcome the UTE
problem? This is even less of an issue. We recall that UTE states that
there may arise situations in which we have two theories, both
equally supported by the evidence, and hence we cannot believe
either theory to be true. Indeed, says the constructive empiricist, nor
should we! Nevertheless, we can accept both theories as empirically
adequate. Of course, as a practising scientist, you may have to
choose to work on one rather than the other simply because you
don’t have enough funding or expertise to work on both. Or you may
decide that one is simpler, or easier to work with, than the other.
That’s all fine; the reasons for your choice have nothing to do with
the truth of either theory. The choice to work with one or the other
will be made on purely ‘pragmatic’ grounds.
Finally, what about explaining the success of science? Obviously,
the constructive empiricist will not go with the NMA. Instead, she
might question the sense in which, without the NMA, the success of
science would be a miracle. As we noted at the end of the last
chapter, this success appears striking but perhaps that is only
because we focus on the successful theories and forget about all the
others that fell by the wayside. Take a stroll through the university
library sometime, run your fingers along the bound and collected
volumes of the Journal of Neurophysiology, or The Physical Review
or The Journal of Chemical Ecology or any one of the many special-
ist scientific journals, and pull out one of the dusty volumes from the
early years. Just look at all the theories and hypotheses that were
proposed but have subsequently been abandoned. Many of them, of
course, were immature, half-baked even, but given such a plethora,
is it any wonder that sometimes, some of them get it right?
Compare this, again, with the situation in biology: through muta-
tions or recombinations, the DNA of an organism changes. These
changes can be beneficial, harmful or neutral. If harmful, given a
particular local environment, it may be unlikely that the offspring
that inherit that mutation will themselves survive to reproduce and
so the mutation dies out. If beneficial, again in the context of a par-
ticular environment, it may confer some advantage on the organisms
that inherit it and hence the mutation spreads. As this process con-
tinues, entirely new species will form and we end up with the fox,
which can live just about anywhere from the tundra to urban parks
and can eat just about anything, and we think, ‘Wow, This species is
amazingly successful.’ But it only seems miraculous if we forget
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ANTI-REALISM
about all the evolutionary false starts due to harmful mutations
along the way. The actual explanation is rather prosaic: there were
lots of changes, only a few of which were beneficial, and those are
the ones we notice. It’s the same with scientific theories: we tend to
forget all the false starts and falsified hypotheses and by isolating the
really successful ones treat that success as something in need of a
realist explanation.
So, let’s sum up the core ideas of constructive empiricism:
1) We have knowledge only of the observable (this is the empiricist
feature), where what is observable is what could be observed by
the naked eye in principle, that is, as described and understood
by science itself. (So, for example, Jupiter’s moons are observable,
because science tells us that we could travel out beyond the aster-
oid belt and observe them with the naked eye; electrons are not
observable because, despite certain cheesy science-fiction movies,
science itself tells us that we could never shrink down to see them
with our own eyes).
2) Unobservable entities and processes may exist but we can never
know.
3) Theories may be true but we can never know.
4) Theories may nevertheless be accepted as empirically adequate.
5) Empirical adequacy, not truth, is the aim of science.
Now hopefully I’ve convinced you that this is an interesting view
and, more than that, a viable alternative to realism. However, it too
faces problems:
First of all, as we have just emphasised, it is grounded on the idea
that we can have knowledge only of that which is observable with the
naked eye. Now you might object that this relies on making a clear
distinction between the observable and unobservable, one that we
may have real trouble actually making. In times past, philosophers
tried to draw the distinction in linguistic terms, between observation
statements and theoretical ones, but gave it up as hopeless. The
modern constructive empiricist doesn’t think the distinction can be
drawn that way, but rather in terms of the entities themselves. So,
we’re observable, and so are Jupiter’s moons, but electrons are not. In
between we might encounter a grey area where it’s just not clear
whether the entity concerned – very large molecules perhaps, or
very small bugs – count as observable. But that just means that
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SCIENCE: KEY CONCEPTS IN PHILOSOPHY
‘observable’ is a vague term (like ‘bald’), and as long as we have a
good idea of when it can be employed and when not, there shouldn’t
be any problems.
More significantly, perhaps, you might feel that taking ‘observable’
to mean ‘observable with the naked eye’ is just way too restrictive.
What about the use of instruments like the microscope? Don’t scien-
tists talk of ‘observing’ things through such instruments? Indeed, as
we have noted, they even talk of ‘directly observing’ the core of the
sun using highly specialised detectors that record the flux of sub-
atomic particles known as neutrinos. However, this is where the con-
structive empiricist reminds us of that second term in her name – she
is an empiricist and that means taking a particular stance with regard
to what counts as knowledge, one that emphasises the role of experi-
ence, whether that be understood in terms of sensory data, or is
extended to include the connections between these data. To insist that
you have a broader understanding of ‘experience’ is just to adopt a
different stance and if the constructive empiricist can account for
everything you can, in particular if she can account for scientific
practice, and, moreover, avoid the PMI and UTE problems, then it’s
not clear on what grounds you can say that your stance is better!
But what if we were to perform some Frankenstein type experiment
and replace someone’s eyes with twin electron microscopes? Such a
person could presumably claim to ‘observe’ bacteria, the crystalline
structure of various surfaces, even clusters of atoms (the ‘Size and Scale’
website (http://invsee.asu.edu/Modules/size&scale/unit3/unit3.htm)
even categorises this under ‘New Sets of Eyes’). Or imagine that the
SETI project finally pays off and we find ourselves in contact with an
alien species whose eyes have evolved differently so they can see to a level
that we can’t (just as birds, for example, can see polarised light that we
can’t). Doesn’t that suggest that the constructive empiricists’ distinction
between what is observable and what is not is somewhat arbitrary?
The constructive empiricist answers as follows. We need to be
clear that when we look at the beautiful images produced by a scan-
ning tunnelling microscope, we are looking at images that have been
produced by a physical process very, very different from the impact
of light on the human eye, one that involves the ‘tunnelling’ of elec-
trons between the surface of the body and a tip so sharp it consists
of just a single atom, producing an electrical signal that is kept con-
stant by raising and lowering this tip, and this raising and lowering
is then recorded and enhanced by computer to yield an image.61 So
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ANTI-REALISM
our Frankenstein operation would have to involve a bit more work
than simply plucking out someone’s eyes and replacing them with an
instrument like this, and any alien that ‘sees’ via such a process
would have to have a very different physiology from ours. Indeed, the
constructive empiricist would insist, it would be so different that we
would have to conclude that such aliens, or the results of our mon-
strous experiment, could not be counted as a part of our ‘knowledge
community’, in the sense that what counts as knowledge for them
would have to be very different from what it is for us.
The second major problem has to do with the explanation for the
success of science. We saw that this provides the motivation for
realism, through the NMA. Now is the Darwinian explanation of
the success of science offered by the constructive empiricist itself
adequate? Let’s return to the analogy with evolution and ‘survival of
the fittest’. The underlying notion of the ‘fitness’ of a species is now
understood in genetic terms, as we indicated in our sketch above.
What would correspond to such terms for a theory! Let me put it
another way: we now understand how a particular species, like the
European fox, for example, is so successful in terms of the interac-
tion between, ultimately, genetic changes and the particular envir-
onment the foxes’ evolutionary ancestors found themselves in. The
‘environment’ for a theory might be taken as the empirical world,
with experimental results leading to the extinction of certain theo-
ries and allowing the survival of others. But what would count as the
underlying mechanism, analogous to the genetic make-up of an
organism that drives the changes in theories? It’s hard to see that
there could be any such mechanism and so the analogy begins to
look a bit ropey. The realist, of course, has an answer: a given theory
is successful in that particular empirical environment because it has,
in a sense, latched on to the world; it has ‘got’ the world right.
ALTERNATIVE 2: ENTITY REALISM
Even if you agree that constructive empiricism is too sceptical a
stance and too restrictive in what counts as knowledge, you might be
reluctant to return to full-blown realism. Is there no more modest
form of realism that satisfies the feeling that we can know how the
world is, in both observable and unobservable terms, and solves the
problems faced by its bloated cousin? Here’s another alternative that
might do the trick.
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First of all, let’s recall that the source of the PMI problem is the
apparent abandonment of certain unobservable entities throughout
history; and the source of the UTE problem is the focus on the truth
of theories. The view known as ‘Entity Realism’ (a view developed
by Hacking and nicely described in his book, Representing and
Intervening) offers a way through these difficulties by urging us to
tear our philosophical attention away from theories and the thorny
issue of whether they can be held as true or not, or might be true
only we can never know it, or whatever, and instead focus on those
unobservable entities that we are confident exist, not because they
are presupposed by some theory, but because we use them. It’s this
pragmatic feature of entity realism that marks it out from other posi-
tions in the realism-anti-realism debate. The core ideas, then, are the
following:
1) Some entities are retained through scientific change; e.g., the elec-
tron, the gene . . .
2) Our belief that these entities exist has nothing to do with the truth
of theories, but with their practical manipulation in the creation
of phenomena.
Here’s what Hacking says:
Experimental physics provides the strongest evidence for sci-
entific realism. Entities that in principle cannot be observed are
regularly manipulated to produce new phenomena and to inves-
tigate other aspects of nature. They are tools, instruments not for
thinking but for doing. . . . The experimentalist does not believe
in electrons because . . . they ‘save the phenomena’. On the con-
trary, we believe in them because we use them to create new phe-
nomena.62
He gives the example of scientists spraying a stream of electrons at
a tiny niobium ball in order to change its charge in an experiment to
detect the presence of sub-nuclear particles called quarks. We don’t
need to bother with the details of the experiment; what is important
is the fact that the electrons are regarded as nothing more than just
a tool which the scientists manipulate to create a new phenomenon.
This has given rise to a famous slogan summarising Hacking’s view:
if you can spray ’em, they’re real! The electrons are just something
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ANTI-REALISM
that can be more or less taken down off the shelf and used to achieve
the desired effect. And just as the car mechanic doesn’t fret over
whether her wrench is real or not (at least not unless she’s taken some
philosophy classes), so the scientist doesn’t and shouldn’t worry
about the reality of electrons and other unobservables.
Now, how does this position overcome the PMI problem? Well,
the entity realist certainly acknowledges the issue and accepts that
there is some change throughout the history of science at the level
of unobservables; but the point of the PMI argument was to cut
the realist’s link between the empirical success of theories and
belief in the existence of the entities posited by those theories. The
theory that posited that heat was a kind of substance, called
caloric, certainly enjoyed some significant empirical success but
we now accept that heat is just molecular motion and there is no
caloric. Nevertheless, there is also retention of certain entities at
this level and thus we have grounds for optimism, but these
grounds have nothing to do with the empirical success of the
associated theories; rather they have to do with the use to which
these entities are put. Consider the humble electron again: the
associated theories have changed quite radically, from theories
which took electrons to obey the classical mechanics of Newton,
to the new quantum theory which suggested they had a wave-like
aspect, to quantum electrodynamics which presents them as
simply bumps in a quantum field, to today’s string theories and so
on. Despite all these changes, scientists have continued to believe
in the existence of electrons because they have become an indis-
pensable tool.
So, how does entity realism overcome the UTE problem? This is
even easier to tackle. We recall that UTE insists that of two theories
supported by the same evidence, we cannot believe either theory to
be true, hence we cannot believe in either of the entities posited by
the theories. Well, as we’ve seen, entity realism argues that belief in
the existence of certain entities has nothing to do with belief in the
truth of the associated theories. Indeed, Hacking maintains that
scientists typically use different or even incompatible models of the
electron, for example, without worrying about the truth. We can
still believe that such entities exist even when faced with UTE-type
situations.
Finally, then, how does this view explain the success of science?
Remember, for the realist this is really important. She employs the
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SCIENCE: KEY CONCEPTS IN PHILOSOPHY
same argumentative strategy as scientists themselves, or so she
claims: namely, we take the best explanation of the phenomenon at
hand and regard that as the truth. In the case of science, the phe-
nomenon might be the bending of starlight around the sun, for
example, and the theory would be Einstein’s General Theory of
Relativity; in the case of the philosophy of science, the ‘phenome-
non’ is the success of science itself and the ‘theory’ is realism.
However, the entity realist just isn’t interested in the supposed truth
of theories as this is not indicative for what we should take as ‘real’.
As we’ve already said, the empirical success of theories can be mis-
leading, leading scientists to accept the existence of entities subse-
quently shown not to exist. The entity realist has a different view of
success: science should be deemed successful not because it allows
us to better represent the world, and say how the world is, but
because it allows us to intervene in the world, by, for example, creat-
ing new phenomena and new technologies. It is intervention and not
representation that we should be focusing on and it is the fact that
we can use them as tools for intervention that leads us to believe in
electrons and other unobservable entities.
Now, this is a powerful and quite complex view but it too faces
certain problems.
First of all, it has an obviously unpalatable consequence; what if
you’re faced with an entity, or rather, with a hypothesis positing an
entity, which you can’t manipulate, and can’t use to intervene in the
world? The entity realist would presumably have to insist that you
have no good grounds for taking this entity to exist. Now, stepping
outside of the domain of physics for a moment, that may not present
much of a problem for the chemist, say, since she can argue that as
she uses certain kinds of molecules to produce certain effects and
create certain kinds of phenomena, she can claim these molecules
exist. Likewise, the biologist who uses certain enzymes to snip
strands of RNA into pieces in order to create certain genetic phe-
nomena has grounds for regarding these enzymes, at least, at real.
But what about the psychologist who talks about the ego, say? They
seem to be on much thinner ice. Perhaps that’s a good thing, perhaps
this is a way of winnowing out all the ‘dodgy’ entities and leaving
only those we really should take as real (really real!).
But even in physics, or rather astrophysics, there may be problems.
Astrophysicists have noticed a kind of phenomenon whereby very
similar objects appear to be symmetrically reproduced across certain
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ANTI-REALISM
regions of space. Consider, for example, the ‘Einstein Cross’, where
a ‘cloverleaf’ of four bright spots can be seen at the centre of a
distant galaxy.63 Now, most galaxies have only one nucleus, so this is
an odd phenomenon and astronomers have tried to explain it by
suggesting that in fact what we’re seeing is the light from a far distant
object known as a ‘quasar’, which is bent and split by the gravita-
tional field of the intervening galaxy to produce four images. The
galaxy is acting as a ‘gravitational lens’.64
Now, many astronomers have come to accept the existence of
these gravitational lenses because they explain a number of other-
wise bizarre phenomena. And it’s easy to see how the explanation
goes: here’s something really odd – four bright spots at the heart of
a galaxy, for example. The chances that this is just a galaxy with a
very unusual heart are really low; a better explanation – indeed, the
best one – is that we’re seeing another gravitational effect: the mass
of the galaxy is so huge that it distorts the surrounding space-time
sufficiently to refract and bend the light of a distant object, creating
the four images. However, as far as the entity realist is concerned,
this is not good enough; we cannot believe in the existence of gravi-
tational lenses until we can use them and manipulate them to
produce new phenomena. Now what are the chances that we’re
going to be able to use the centre of a galaxy the way a mechanic uses
a wrench, any time in the future?! This puts the entity realist out of
step with the top scientists in astrophysics, but perhaps that’s a bullet
she’s prepared to bite.
That’s not the only objection, however. The entity realist accepts
that electrons, genes, etc. (but not gravitational lenses, or black
holes), exist; but what are they? If we say, an electron is a charged
sub-atomic particle, or a bump in a quantum field or the vibrating
end of a quantum ‘string’ or whatever, where have we got that
description from? A theory, of course. But how can we say what an
electron, gene, or whatever, is, if our theories about it change, or if
we have incompatible theories about it? As we’ve already noted, our
description of the electron has shifted quite dramatically in the
past hundred years or so, from being a small chunk of matter, to a
wave-particle, to a bump in the Great Quantum Field, to the mani-
festation of a multi-dimensional superstring, to … But if we focus
on these descriptions, we’re faced with something like the return of
PMI! The entity realist might be able to say that electrons exist,
because she can use them like tools, but she can’t say with any
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SCIENCE: KEY CONCEPTS IN PHILOSOPHY
confidence what they are, because history teaches us that our current
description may soon go the way of those held ten, fifty, a hundred
years ago. However, if we can’t say what the electron is, isn’t our
belief that it exists empty?
Again, the entity realist may just have to swallow that and agree
that all she can say is that there’s something out there, it’s charged in
such and such a way, it has the following mass, but that’s all she can
say. Here’s a final objection that many people take to be a real hurdle
that has to be overcome.
The entity realist, as we have seen, focuses on the use scientists
make of certain entities. But are electrons, enzymes and the like
really on a par with a mechanic’s wrench? After all, you can’t actu-
ally pull down a big box of electrons off the shelf and start throwing
them around. What scientists actually do is use an electron gun,
which produces an appropriately focused beam of electrons which
can then be targeted on a niobium ball, or the inside of a TV screen
or computer monitor. It’s the electron gun that is more like a wrench,
to be used by the scientists to achieve the effect they want. Now, the
electrons are unobservable – that’s the crucial issue, of course – so
what the construction and use of the electron gun rely on is an
understanding of certain properties of the electrons (such as charge
and mass) and the laws they obey. These laws may not be super-high
level and abstract, they may be cobbled together in such a way that
they apply only to the particular situations in which the electrons are
produced, but it is these that the scientists rely on. In other words,
the scientists must accept these low-level laws as true in order to
achieve the effects they want. So, when we use electrons, say, to create
new phenomena, we’re relying on the truth of ‘low-level’ (causal)
theories about electron behaviour. And these low-level laws and the-
ories are accepted as true because they are empirically successful.
But if we focus on these low-level laws, we’re faced with something
like the return of UTE! Suddenly entity realism doesn’t look that
different from the more standard form.
These sorts of objections haven’t ruled the position out and many
philosophers of science continue to develop it, particularly those
who feel that the analysis of science tends to be too theory oriented
and needs to focus more on pragmatic and experimental matters.
However, there is another form of realism that goes to the other
extreme and embraces the theoretical. Let’s take a look at that before
we move on.
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ANTI-REALISM
ALTERNATIVE 3: STRUCTURAL REALISM
Let’s go back to the PMI and look a little more closely at the history
of science. And let’s take another example: the history of light.
Newton famously thought light was composed of tiny particles that
underwent ‘fits’ when they passed from, say, air to glass, leading to
the phenomenon of refraction. Then Young proposed that light is in
fact a wave and Fresnel developed this theory further, producing a
set of equations (now known as, surprise, surprise, the Fresnel
Equations) which describe the behaviour of light when it passes
from one medium – air, for example – to another – glass, say. We
recall that when a critic pointed out that if light really was a wave,
under the right conditions we should see a white dot in the shadow
cast by an illuminated disc (due to diffraction around the edges of
the disc), Fresnel ran the experiment and was as surprised as the
critic when a white spot was observed. Maxwell brought light under
the umbrella of his theory of electromagnetism (remember Hertz’s
experiments?) according to which it was conceived as an oscillating
electromagnetic wave. Then came quantum theory and Einstein
(again) argued that light had to be seen (!) as possessing particle-like
qualities, so that it demonstrated the famous quantum wave-parti-
cle duality. Subsequently it too was regarded as a kind of quantum
field, and so the story of its changing nature continues.
Now this looks like nice grist to the PMI mill: light as a
Newtonian particle has been abandoned, as has light as a wave, so
we have no good reason to suppose that in future years, the idea of
light as a quantum field will also be consigned to the dustbin of
history. But perhaps this is too hasty. Perhaps there is something that
is retained throughout these dramatic theoretical shifts, something
more than just all the empirical evidence that the constructive
empiricist focuses on. After all, we still use Maxwell’s equations (in
certain circumstances) in the quantum era, and even after Maxwell
proposed his theory, scientists still used Fresnel’s equations. Indeed,
they drop out of, or, more precisely, can be deduced from Maxwell’s
theory if certain conditions are applied, and in this sense they are
retained despite all the shifts in our views of what light actually is.
These equations can be understood as representing the underlying
structure of reality and the view that structure is what is retained
through theory change and is what we should be realists about, is
known as structural realism. Its core ideas are as follows:
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SCIENCE: KEY CONCEPTS IN PHILOSOPHY
1) Structure is retained through scientific change.
2) Structure is what we should be realists about.
This is actually quite an old idea and if you look back through the
last hundred years or so of commentaries on science, you find it crop-
ping up again and again. Poincare, for example, was a famous (and
brilliant) mathematician and physicist (he came within a whisker of
discovering the theory of relativity, for example), who also thought
deeply about the nature of science. He also noted that certain equa-
tions are typically retained through theory change and wrote,
. . . if the equations remain true, it is because the relations pre-
serve their reality. They teach us now, as they did then, that there
is such and such a relation between this thing and that; only the
something which we then called motion, we now call electric
current. But these are merely names of the images we substituted
for the real objects which Nature will hide for ever from our eyes.
The true relations between these real objects are the only reality
we can attain.65
The idea then, is that all that we can know about reality is captured
by the equations representing the relations between things, whose true
‘natures’ we can never really know (so to that extent the PMI is right).
How does this view overcome the PMI problem? Well, the answer
should be obvious: PMI insists there is radical change at the level of
unobservable entities; but it overlooks the fact that there is also
retention of certain structures at this level. Shifting our attention
away from the entities and on to the structures, it is the latter we
should be realists about.
How does this view overcome the UTE problem? This is a little
trickier, but one response runs as follows: UTE is supposed to lead
us to conclude that we cannot believe either theory to be true, but
that’s OK, because the structural realist doesn’t take the entire
theory to be true, just those structural aspects that are retained
through theory change. So, the structural realist will insist that in
order for both theories to be empirically successful, they’re going to
have to possess certain equations or structures in common and it’s
that common part we should believe. Now, if the anti-realist
can come up with examples of UTE where there are no common
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ANTI-REALISM
(structural) parts beyond the empirical level, then the structural
realist will be scuppered. The extinction of the dinosaurs could be
one example, although the structural realist will follow the ordinary
realist in arguing that further evidence will surely settle that case one
way or the other.
Finally, how does this view explain the success of science? Here
the structural realist typically follows his non-structural cousin and
argues that the success of science gives us good reason to suppose
that our theories correctly describe the world, at least with regard to
its structural aspects. In this sense the structural realist wants to
present herself as less radical than the constructive empiricist and
not as restrictive in her beliefs as the entity realist.
Now, as we noted above, this form of structural realism holds that
all we can know is the structure of the world and we just have to
remain agnostic about the nature of the entities. There is another
strand, however, which insists that it is not that all we know is struc-
ture, but all there is, is structure. The motivation for this is quantum
physics. A proponent of the above form of structural realism wrote
that 4[t]he structural realist simply asserts . . . that in view of the
theory’s enormous empirical success, the structure of the universe is
(probably) something like quantum mechanical’.66 But according to
quantum physics, the ‘nature’ of the entities of the world as objects
is deeply problematic. This is something the original heroes of the
quantum revolution spotted and they noted that, according to the
theory, the fundamental entities could not be regarded as individual
objects, in the way that tables, chairs and people can. That’s proba-
bly enough to make you wonder about the nature of these entities.
It turns out, however, that the theory is consistent with the frame-
work of individual objects. So now it appears we have another kind
of fundamental underdetermination, only this time with the theory
supporting two very different basic interpretations: in one the enti-
ties of the theory are individual objects, in the other they are not, in
some sense. Anti-realists such as the constructive empiricist allege
that this raises yet another problem for the ‘standard’ realist, since if
she can’t even say whether the objects she believes exist are individ-
uals or not, what good is her realism?
This second form of structural realism responds to this challenge
by suggesting that we should drop the notion of object from our
theory altogether, so that what theories are about, on this view, are
nothing but structures, pure and simple. Well, perhaps not so simple
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SCIENCE: KEY CONCEPTS IN PHILOSOPHY
as it is not entirely clear what it could mean to say that the world is
fundamentally just structure. A common understanding of a struc-
ture is that it consists of a family of relations holding over a set of
objects. So, consider the genealogical structure of your family, with
relations such as ‘father of and ‘daughter of holding between
various people. But if the objects are removed from the picture, what
do the relations hold between? And how can relations hold without
any relata? These are crucial questions but to go any further would
take us way over the cutting-edge and into the abyss! All I can say at
this point is that explicating this form of structural realism is the top
priority for these structural realists (such as the author!).
As with the other positions, structural realism also faces prob-
lems. First, in its focus on mathematical equations, this position
seems to be oriented towards the more mathematical sciences, such
as physics. What about biology, or even psychology, where there is
much less mathematisation? Can structural realism find a place in
these fields too? One answer is a blunt ‘yes’, since the notion of struc-
ture is broad enough that one can argue that maths is just one way
of representing it. However, there is a lot more work to be done in
developing structural realism in a biological context, say.
A second problem is associated with the question, is it always the
case that structure is retained through theory change? What if the
structures themselves change? If that happens, then we’ve lost one
of the main advantages of going structural, which is to respond to
the PMI. However, even granted that there has to be some change
for science to progress, its not clear that the structures the realist is
interested in change so radically that structural realism is fatally
undermined. Finally, however, doesn’t the above response to the
UTE problem assume precisely what the realist needs to show! It
merely expresses the hope that in any such cases, there will always be
common structure. But what if two such empirically equivalent the-
ories don’t have any structure in common? Then we would see the
return of UTE as well. As in the previous problem, what we need to
see are some concrete examples, and these have not been forthcom-
ing, at least not so far.
CONCLUSION
There are a variety of views on offer. The ones I’ve covered here –
standard realism, constructive empiricism, entity realism and
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ANTI-REALISM
structural realism – are just some of the more well known. Which
one you think is the ‘best’ account will depend not only on your
understanding of scientific practice, its aims and its history but also
on your philosophical views about what we can know. Any argument
in favour of one position runs the risk of ‘begging the question’
against the others. All I’ve tried to do here is sketch the main
arguments for and against, and bring you up close to the ‘cutting-
edge’ in this area. Now we’re going to consider a broader form of
anti-realism, one that gets its force from the suggestion that scientific
practice and, in particular, scientific change and progress, are not
driven by observations and empirical support, but by social, polit-
ical or economic factors.
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Study Exercise 3: Truth and Existence
Consider the following questions:
Do you think bacteria exist? Why?/Why not?
Do you think genes exist? Why?/Why not?
Do you think electrons exist? (here it comes . . .) Why?/Why not?
Write your reasons down in each case. Are they the same sorts of
reasons in each case or do they differ in some respect? Do you think
any of these reasons are better than any of the others? If so, give
reasons why you think they are better.
Now consider the following:
There has been a huge discussion in recent years over the question
of whether there is life on Mars. Not the evil aliens portrayed in
War of the Worlds, but very simple life at the bacterial level. The
discussion is important not simply because it’s an interesting ques-
tion whether life exists on other planets, but also because it has
been suggested that life on Earth itself might be a by-product of
life on Mars, as chunks of rock were blasted off the planet’s surface
by asteroid impact, carrying tiny hitch-hikers across the void.
In 1996, NASA claimed to have discovered ‘nano-fossils’ –
fossils of very small bacteria – in a meteorite that is known to have
come from our neighbouring planet. A year later, NASA’s Mars
probe detected evidence that there had once been water flowing
there, and if there was water, there had to have been an atmos-
phere as well. Further evidence has been produced showing chan-
nels shaped by water flow, as well as the possibility of large tracts
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Technical Requirements of the Journal Entry:
· Microsoft x (not .pages or )
· Double Spaced, 12 pt. Times new Roman Font, 1″ Left and Right Margins
· Minimum 500 words
Week Seven Journal Prompts:
Write about one or more of these prompts for your journal entry this week.
· In what ways do I trust science to tell me the truth of reality?
· Is science important to me ethically?
· If I question science, am I questioning the nature of reality?
· If I am committed to strong scientific realism, what would happen if I questioned these commitments?
· Will science never find the truth of reality?
(1) C
hakravartty, Anjan, “Scientific Realism.” Stanford Encyclopedia of Philosophy. Plato.stanford.edu (2017)
An excellent overview of the issues and definitions of scientific realism.
(2)
Liston, Michael, “Scientific Realism and Antirealism.” Internet Encyclopedia of Philosophy. Iep.utm.edu (2020)
A good overview of the realism / anti-realism debate.
(3) Musgrace, Alan, “The ‘Miracle Argument’ For Scientific Realism.” The Rutherford Journal, rutherfordjournal.org (2008)
An overview of the No Miracles Argument for Scientific Realism using historical examples.
(4) S
tanford, Kyle, “Underdetermination of Scientific Theory.” Stanford Encyclopedia of Philosophy. plato.stanford.edu (2017)
A good overview of the underdetermination of theory by evidence argument for scientific realism
(1) “What is Scientific Realism?” YouTube, uploaded by Carneades.org, Oct 18, 2015. [5:53]
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