Can scientific theories describe an unobservable reality underlying the phenomena?
Theoretical claims in science concerning unobservable entities, such as electrons, have sparked an on going debate between realism: the notion that such unobservable entities are real, and anti-realism: the notion that they are not real[*].
This essay will firstly outline a general definition of a scientific theory before moving on to give a brief account of Bas Van Fraassen’s theory of constructive empiricism.
Lastly, this paper will attempt to argue against this theory by claiming and concluding that the progress and success of science provide us with a good reason to believe that such entities are real.
What is a scientific theory? It is a scientific model which follows a specific cycle. Firstly, some regularity in nature is observed before theories are inferred from observation. In the majority of cases, scientific theories often postulate entities that are unobservable but deemed real by realists. However, anti-realists disagree; they argue instead that such entities are not real.
One such anti-realist is Bas Van Fraassen. He argues that, contrary to the realist position, the aim of science is not literal truth. Hence accepting a scientific judgement or theoretical position entails that one suspends judgement of the term. For Van Fraasen ‘a scientific theory is empirically adequate exactly if what it says about the observable things and events in this world is true – exactly if it saves the phenomena’. This is Van Fraassen’s own version of anti-realism, and he calls it ‘constructive empiricism’. Scientific theories, for Van Fraassen, are only empirically adequate if it can explain observables in the phenomenal realm. Therefore, we cannot know and should not excite any tendency toward any entity beyond the ‘realm’ of observables.
Van Fraassen makes a pseudo-Kantian distinction between an observable and unobservable realm[†], and claims that it is ‘naïve’ to think that the entities postulated by theories are real things. For example, in 1897 J.J Thompson theorized that the only sound explanation for the behaviour of cathode rays was down to tiny charged particles called electrons. Although they were inherently unobservable, the electron provided the best explanation for the behaviour of such rays. Though electrons are inherently unobservable, physicists take such entities seriously and consider them as real entities though not strictly observable. They are not agnostic about them since they have reason to believe that such things are real in the world (beyond the phenomenon).
One of the reasons they have this belief is because they believe such theories are successful, to a certain extent, in explaining observable phenomena[‡]. For example, Einstein’s theory of relativity has been deemed successful in explaining how gravity operates even though we cannot observe gravity directly as something observable in itself. Of course, this is not to say that the theory is perfectly accurate, it may well not be. But generally speaking, it doesn’t matter whether theories such as these are completely accurate – indeed can this be ever the case? – what matters is that they tend toward, or converge to a high degree of accuracy. Contrary to both Van Fraassen’s claim that science aims to describe literal truths and Laudan’s assertion that because the history of science is packed with successful but incorrect theories, it is wrong to suggest that these theories refer to real entities; these arguments do not show that entities postulated by scientific theories are not real and neither do they suggest that as a result we should propose an agnostic stance toward them. Scientists must always allow for misinterpretations or miscalculations of the thing in question. This could well be due to a lack of understanding the entity or due to the current limitations of technology that inhibit us in gaining a deeper insight into them.
What is important is that theories are converging toward, or, at least, tracking[§] the truth within a certain degree of accuracy. Van Fraassen’s claim that science aims for literal or complete truth is far too strong an assumption for realists to take seriously.
Others such as McMullin have argued that scientific theories are progressively successful in terms of their fertility: they are productive and inventive, and that they bring with them many avenues for further development. This seems to suggest that ‘structures postulated by the theory correspond reasonably well to the structures of the real’. Because we have theories that postulate entities like quarks, dark matter, and protons; their power of explanation leads us to believe in a reality underlying our level of the phenomenon[**].
Admittedly, Van Fraassen would probably claim that such theories are fertile, or tracking the truth only in an empirically adequate way; that is, they are tracking the truth within the realm of observational entities, and not tracking the truth in terms of these unobservable ones.
But what does he mean by observable? In Van Fraassen’s words: ‘all observable phenomenon are as if there is a mouse in the house”, meaning that we should only be concerned with theories that help us explain the observable entities in question.
But suppose we take Van Fraassen to his word and observe a mouse that just happened to trot along the floor while I write this essay. Does this stop me from inferring further things about the mouse? Suppose I infer that the mouse has lungs. Should I be agnostic because they are inherently unobservable to the naked eye? No, of course not. Although I cannot observe the mouse’s lungs directly, I can detect them if I look closer, for example from its breathing.
We can also extrapolate this analogy to a more scientific example like our electrons. Although no one has ever observed them directly since their discovery in 1897, we are still able to detect them and use this knowledge to create things like computers. Therefore, given the choice between agnosticism or the belief that they are real features of the world it is entirely rational to assume the latter.
Hilary Putnam argues similarly, that if we don’t at least believe in the reality of such entities, then the fact that they can explain things would be miraculous. Although Van Fraassen agrees that the success of science cannot be miraculous, he instead offers a Darwinian explanation for their success. Like organisms, scientific theories struggle for survival, and therefore, the ones that survive are the ones that are successful in explaining the phenomena, while the others die away. It is inevitable then, that the theories that survive are the successful ones. Although it is difficult to compare the likes of an organism to a scientific theory, it is my interpretation that Van Fraassen is accepting the theory of evolution as only ‘empirically adequate’ without believing its truth. This is surely problematic; for if he doesn’t believe in its truth, then how can he use it confidently to explain the success of scientific theories? Van Fraassen must have a belief, vague or otherwise, in the power of evolutionary processes, even though such processes are inherently unobservable. I see no reason how one can accept a theory, use it for argumentation or to make a point without actually holding a believing in them. Any element of belief surely deviates, one way or another, from strict agnosticism.
In this sense, I see no problem with scientific theories attempting to describe an unobservable reality behind the phenomena. I say it is attempting to describe because it is impossible to be absolutely certain that theories are completely accurate. Nevertheless, this element of scepticism should not necessarily lead us to agnosticism, for there is much reason to believe that unobservable things are real in an implicit sense - scientific progress shows this.
No doubt, many physicists today would claim that things such as electrons and other small particles like photons are now part of our phenomenal world; since machines can now detect them. In the past, such entities were undetectable and hence no scientific indication for their existence could be put forward, but that didn’t mean that they didn’t exist at that time. Over time, then, unobservable things shift to being observable. If that is so, is Van Fraassen justified in making such a distinction between them in the first place? Grover Maxwell argues that we have no criteria in drawing such a line since there is a continuous state of transition between them.
Maxwell is saying that everything in the universe has the potential of being observed at one time or another. For example, we can observe and detect things far out in the cosmos now which the ancients could never have done, but the potential for observing these things have always been possible.
Van Fraassen argues against Maxwell by claiming that such a distinction is possible. He gives an example of a charged particle traversing inside a cloud chamber. While travelling it leaves behind a trail. Van Fraassen states that ‘while the particle is detectable by means of the cloud chamber, and the detection is based on observation, it is clearly not a case of the particle being observed’. Admittedly, we can’t observe such small particles with the naked eye, however if the aid of instrumentation provides us with a certain amount of confidence in that something is causing this trail, then is it not reasonable to assume that there is something real going on? What is interesting about this example is that Van Fraassen is perhaps inexplicably admitting that the cause of this trail is due to a charged particle although he cannot ‘see’ it directly. Such a claim, then, is not a totally agnostic one; it would seem that the particle is more likely to be a real entity than not.
To summarize, this essay argues against Van Fraassen’s constructive empiricism while arguing that the success of science provides us with grounds for believing, at least, that unobservable entities are real in the sense that science tracks or converges toward truth. It has argued that his agnosticism cannot be totally sustained given the progress of science, and distinctions between what is observable and unobservable. Both provide us with sound reason for the belief that entities postulated by theories are more real than not.
© 2011 Roberto Nacci All Rights Reserved
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[*] In the remainder of this essay, I will take real to mean something that exists in the world as opposed to something imagine or supposed.
[†] Pseudo because, unlike Kant, Van Fraassen does not make the distinction between the world as it appears to be and the world as it really it in reality. He, instead, makes the distinction between observables and unobservable time. But such ‘realms’ exist in space and time.
[‡] Known as: the success of explanation argument.
[§] Tracking the truth is a phrase initially coined by Robert Nozick – knowledge is belief that tracks the truth – since we cannot claim that scientific theories literally describe the truth as complete; instead they track it within a certain degree of accuracy – the history of science shows that progress is being made. See: Robert Nozick, Philosophical Explanations. Harvard University Press. (1981)
[**] Some anti-realist philosophers of science have pointed to the fact that the ether theory (that light travels in a medium named the ether) was never found. Indeed, it is true. But, this could well be due to the lack of understanding the nature of light at the time. But this isn’t so detrimental to realists as it allows, as science progresses, to create more accurate theories that tracks truth.
 Van Fraassen, Bas (1980): ‘Arguments concerning scientific realism’, In Curd & Cover (1998): Philosophy of Science; the central issues, p. 1069
 Laudan, Larry, “A Confutation of Convergent Realism”, Philosophy of Science, 48 (1981), pp. 19 - 49
 McMullin, E. (1976), ‘The fertility of theory and the unit for Appraisal in Science’, in R.S. Cohen, P.K. Feyerabend and M. W. Wartofsky (eds), Essays in Memory of Imre Lakatos, In Robert Seagull, Fertility and Scientific Realism, British Journal of Philosophy of Science, 59, (2008), p.237
 Op cit. Van Fraassen (1980), p.1077
 Putnam, H, (1975), Philosophical papers, Volume 1, Mathematics, Matter and Method, Cambridge: Cambridge University press.
 Grover Maxwell, On the ontological status of theoretical entities, In In Curd & Cover (1998): Philosophy of Science; the central issues, pp. 1055 - 1056
 Op cit. Van Fraassen (1980) p. 1073