PHIL 336 PART 7

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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C o p y r i g h t 2 0 0 7 . C o n t i n u u m .

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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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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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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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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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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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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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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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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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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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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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