Although every paper I write leaves me feeling revolted and miserable, it has been a long time since a paper made me this uncomfortable. After finishing it, I barely even read through it once before hastily printing it out and rushing to school to hand it in. The process of composing this paper was especially unpleasant too—I did read a lot of books: Quine, Dummett, Goodman, Putnam… all sorts of textbooks and handbooks on philosophy of science, metaphysics, epistemology… of course, all in Chinese translation. You ask why I still didn’t look for English materials? First, there wasn’t enough time; second, I really didn’t want to read them. I found that the prose of the vast majority of analytic philosophers simply did not suit my taste at all; I could not get into it. Of course, Wittgenstein doesn’t even count as an analytic philosopher. Skimming them casually could still occasionally stir up my own flashes of inspiration, but if I read them carefully, I felt there was really nothing there—there was plenty of fine-grained analysis, but the things they cared about were simply not the things I cared about. Those issues were not even issues for me in the first place, or else they could have been discussed in a much more lucid and concise way; in that case I really had no motivation to chew on that flavorless piece of chewing gum, unless I purely wanted to train my reading ability. In short, I still ended up using the old method of sweeping through Chinese books, but I really couldn’t get any feeling out of them, and not a single book could be read straight through for more than a small fraction of its length. What I ended up reading also turned out to be useless: first, I really didn’t find any topic that particularly interested me; second, time was just too tight, and if I dragged it out any longer, Teacher Wu’s paper would truly become impossible to finish. So in the end what came to mind was a rather ready-made topic, one I had thought about before, written about before, and discussed in class presentations before, and which also seemed, to Teacher Sun at least, to be a question he had never seriously thought about: namely, the question of how intuitionism explains quantum paradoxes. But once I actually started writing, even half of the introduction filled three thousand characters, so there was really no way to handle it. The requirement was around three thousand characters; though it could be exceeded, it surely shouldn’t be too excessive, right? And time was limited too… In any case, in the end I stitched together a small half of the introduction along with some discussion of quantum mechanics and made this paper, but it still feels fragmented and broken up… and in many places I am still holding back, wanting to say more but not saying it through to the end…
Anyway, sigh, I’ve submitted it, so I guess that’s that! I only hope Teacher Sun will be merciful.
I originally didn’t want to post it on the blog at all, but then I thought that after all I should still stick to the rules of Suixuan, and besides, it counts as a backup too—PS: I found that some article on my computer had somehow gone missing… If it weren’t for the backup on Suixuan, my Marxist philosophy assignment this time would have been completely dead in the water!
How Is a Scientific Realism Possible?
Abstract: This article criticizes the ambiguity of some scientific realist claims, and through a discussion of issues related to quantum mechanics, points out that after quantum mechanics, if the claims of scientific realism are possible at all, then either they must stand in opposition to the mainstream of contemporary science, or they must reexamine the meaning of words such as “real,” rather than uncritically clinging to ordinary modes of understanding. The point of contention between realism and anti-realism should not be a literal yes-or-no answer to questions like “Are electrons real?”; rather, it should be a discussion of the meanings and uses of words such as what an electron is and what reality is.
Keywords: realism anti-realism Copenhagen interpretation
Having survived the entire Western philosophical purge of traditional metaphysics in the early twentieth century, and having witnessed the new face of twentieth-century science represented by quantum mechanics, it is a puzzling thing that “scientific realism” should still flourish in the philosophy of science. Even more regrettable is the fact that many proponents of scientific realism do not seem to realize that they are the ones resisting the mainstream of the age; instead, they take up their position in the defensive posture as a matter of course, viewing anti-realists as heretics. In fact, after the baptism of the new philosophy and the new mechanics, classical scientific realism long ago lost its footing and perhaps can only struggle to survive in the cracks. Or rather, classical realism should long since have adapted flexibly and reclarified the meaning of “reality” — in that case, some doctrines currently labeled “anti-realism” could also be properly called a kind of realism; why not? This may be a rhetorical strategy: if one always insists on calling only a certain naive and narrow claim “realism,” while lumping together all the rest of the various doctrines, from extreme absolutism to extreme relativism and every variety of moderate position in between, under the blanket term “anti-realism,” then not only will this obscure the real point of contention, it will also make it easy for nihilists to profit from the confusion.
The question this article will discuss is: how, exactly, is the claim known as scientific realism supposed to be possible? That is to say, apart from empty tautologies or emotional venting, what distinctive claims can scientific realism actually put forward?
As for the claim of “scientific realism,” a typical summary is: “It holds that scientific posits or theoretical entities, such as electrons, quarks, etc., have a real existence independent of the human mind, and that the universals of science are abstractions from facts….” [1] A more rigorous formulation would be: “Most of the basic unobservable entities in successful contemporary scientific theories exist independently of the mind.” [2] But for the sake of brevity, let us say that “electrons are real” is the basic claim of scientific realism.
But merely stating such a claim is meaningless. No one would deny that the reason “electron” is called “electron” rather than “dumpling” depends on human institutions and conventions; many anti-realists also do not deny that once one selects a definite mode of observation, the “behavior” of electrons is independent of human intention. The key lies in what role human beings actually play in the construction of scientific theories.
What, after all, does “independent of the mind” mean? What does “real existence” mean? These concepts themselves are highly suspect. In fact, the point of contention between anti-realism and realism should never be “whether electrons ‘are’ or ‘are not’ real,” but rather: “When you say something is ‘real’ or ‘independent,’ what does that mean?” If the concept of “real” is arbitrarily stipulated, then why can I not interpret “a theoretical term is real” as “the term is useful as a theoretical tool”? If so, then what is the difference between realism and instrumentalism?
Regrettably, consciously or unconsciously, some scientific realists really do understand the concept of “truth” in just this way. Alexander Bird, in his textbook on philosophy of science, lists five typical claims of scientific realists [3]:
(a) theories can be evaluated according to their truth or degree of approximation to truth;
(b) the obvious aim of a theory is its truth or approximation to truth;
(c) the success of a theory is evidence in support of its truth;
(d) if theories are true, then the unobservable entities they posit will really exist;
(e) if theories are true, then they will account for observable phenomena.
These five claims sound quite serious, but after all the circling around, they never clarify what this “truth” actually means. According to (a) and (b), the “success” or not of a theory is evaluated by whether it approaches truth; but according to (c) and (e), the “truth” of a theory is inferred through its success. “Success” and “truth” are tied together and mutually reinforce each other, but beyond tautology, what meaningful information do these claims provide? If the judgment of “success” is in fact based on the real status that science has attained in contemporary society, then isn’t this social constructivism? Realists invoke the magical word “truth,” which is in fact just a synonym for “success,” to explain success, and with this “one leaf obscuring the eye” they seem to draw a boundary with instrumentalism or social constructivism; but in substance, aren’t they the same thing? Remove this self-deceiving leaf, and scientific realism and social constructivism are identical in form.
Thus, if the claim of scientific realism still has any meaning, the point lies only in the fourth item: “(d) if theories are true, then the unobservable entities they posit will really exist.” In other words, the point still lies in the aforementioned sentence: “electrons are real.”
That is to say, if a claim of scientific realism is possible, then it must make the sentence “electrons are real” substantive, and here the concept of “real” must be understood in some way that is not merely dependent on “success.”
Some scientific realists understand the concept of “reality” from common sense, and even claim that scientific realism is only possible after accepting common-sense realism [4]. This indeed counts as one possible claim. That is to say, “electrons are real” means “electrons are real in the same way as objects in everyday experience such as stones and tables are real.” However, this claim is obviously suspicious. First, the most powerful critic of “common-sense realism” is not philosophical skepticism, but scientific realism itself. Science provides a picture of the world that is clearly different from common sense and claims that this is the truth about the world. Scientific reality and common-sense reality are, at least on the surface, in conflict. Common-sense realism may well lead to some sort of naive scientific realism, but that does not mean scientific realism is always compatible with common-sense realism. Russell, for example, pointed out: “Naive realism leads to physics, and physics, if true, shows that naive realism is false. Therefore, if naive realism is true, it is false; hence it is false.” [5]
But leaving aside whether physics has in fact refuted common-sense realism, let us examine the concrete meaning of something like “electrons are real in the same way as objects in everyday experience such as stones and tables are real.”
The key point of scientific realism lies in the so-called “independence” of reality, that is, no matter what you think, no matter whether you look or do not look, that stone is “there.” This is of course a very vague formulation; as everyday language we seem to grasp roughly what it means, but how should it be said when applied to electrons? What on earth does it mean to say that some electron is “there” independently of human will?
To answer this, we must first clarify what kind of thing “electrons” are in modern science. Although I am not willing to believe it, it seems that a considerable number of contemporary philosophers of science still retain their notion of “electron” within the framework of classical mechanics, or rather, the framework of common sense — an electron is a tiny, tiny “particle” occupying some definite spatial region, and it is an “unobservable entity” only because it is too small…
But any competent middle-school physics teacher today (or perhaps chemistry teacher) would remind us to be extremely cautious when using our intuitive imagination, because the behavior of “electrons” is in no way intuitively like that of any ordinary thing: it is both particle and wave; it surrounds the atomic nucleus in the form of an “electron cloud”… [6]
What most vividly displays the strangeness of the “electron” is none other than the double-slit interference experiment [7]: when observed midway through, the result is that the electron either passed through slit A or it did not; but when no observation is made, the electron’s behavior on the screen seems to mean that it passed through both A and B at once and interfered with itself…
Given the bizarre behavior of “electrons” in modern science, how exactly are scientific realists going to maintain the reality of electrons? Some scientific realists assume, as a matter of course, that they are allies of contemporary mainstream science, but in fact this is not so. The theoretical terms such as electrons in contemporary physics — that is, in the Copenhagen interpretation of quantum mechanics — are in fact taken up in precisely a kind of interpretation that scientific realists regard as “anti-realist.”
We know that the Copenhagen interpretation of quantum mechanics was proposed primarily by Bohr and Heisenberg. What is its content? A simple way to put it is the so-called “probability interpretation,” but that does not get to the heart of the matter — because all sorts of other interpretations can also, in various ways, acknowledge “probability,” only with different strategies.
Why not look at how Heisenberg himself defined the key difference between the Copenhagen interpretation and its opponents? He said: “All opponents of the Copenhagen interpretation are in agreement on one point. In their opinion, a return to the reality concept of classical physics, or, to use a more common philosophical term, a return to the materialistic ontology, is desirable. They would prefer to return to the concept of an objective world of reality, the smallest parts of which, like stones and trees, exist objectively, whether or not we observe them. However, … this is impossible….” [8]
And what we now see called “scientific realism” is, appropriately enough, precisely that “materialistic ontology.” We can properly say: the essence of the Copenhagen interpretation is not “probability,” but rather “anti-realism.”
At this point it is worth emphasizing again — and this cannot be emphasized too much — where exactly the point of contention between realism and anti-realism lies. It is not about supporting or opposing science, nor about skepticism, and so on. Obviously, Bohr, Heisenberg, and the others were not “anti-science,” nor were they extreme skeptics or relativists. Perhaps it is precisely the so-called scientific realists who are trying to be “anti-science” — at least opposed to mainstream science, for example by resisting quantum mechanics and following Bohmian mechanics [9]. If the location of the disagreement is mistaken, then the anti-scientific side will instead think that its opponent is anti-science, and the whole debate will inevitably become a mess of entanglement and confusion.
Bohr and Heisenberg were both very clear about where the problem lay. Bohr said: “Upon what can we as human beings fundamentally depend? … We depend on our words…. Our task is to communicate to others our experience and our views. We must constantly struggle to extend the range of our description, … ‘reality’ is also a word, a word we must learn to use correctly. … There is no quantum world. There is only an abstract quantum mechanical description. It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature.” [10] Heisenberg said: “Whether one can talk about the atom itself is a physical question, but also a question of language.” [11] Heisenberg repeatedly emphasized: “The Copenhagen interpretation of quantum theory begins with a paradox. It starts from the fact that we describe our experiments in terms of classical physics while at the same time recognizing that these concepts do not fit nature precisely. The opposition between these two points of departure is the root of the statistical character of quantum theory.” [12]
In short, what is the Copenhagen interpretation? In one sentence: it explains the apparent paradoxes of quantum phenomena as “the limitations of human language.” Its point is to break the “illusion” of classical physics, the belief that “we can describe a part of the world without involving ourselves at all.” [13]
So how can a claim of scientific realism be established? The first way is to oppose the orthodox interpretation of quantum mechanics and stand against the front line of contemporary physics; in other words, for example, to follow Bohmian mechanics. Of course, the cost of doing so is that the realist’s habitual talk of “successful arguments” and the like becomes increasingly ineffective. The second way — in a certain sense, the first way also belongs to the second — is to shift the point of contention from metaphysics to linguistics: not to argue over empty questions like “are electrons real,” but to reflect on what words such as “electron” and “real” actually are or ought to mean. Through reflection on words, we should be able to discover that the loss of “reality” does not mean the loss of “objectivity”; and the loss of “objectivity” in some sense does not mean the loss of “certainty”; and some change in the concept of “certainty” does not mean that epistemology will collapse into nihilism. Yet some scientific realists lack the necessary reflection on these distinctions, and still naively bind these concepts together as if they were a single bundle, with the result that they leave an open highway for nihilists behind a weak and powerless shield.
Finally, it is worth mentioning that linguistic research does not need, and should not, arbitrarily assign meanings to concepts without reason. In fact, before scholars’ deliberate work, the way people actually used language was not fixed and unchanging. In other words, one should not simply label a scientist or philosopher a realist or anti-realist on the basis of whether he uses words like “real”; that is meaningless. Heisenberg notes: “I believe that when physicists speak about atomic events, the language they actually use evokes in their minds ideas similar to the concept of ‘potentiality.’ So rather than saying that physicists gradually get used to regarding electron orbits, and the like, as real, it would be better to say that they get used to regarding them as a kind of ‘potentiality.’ At least to some extent, language has adjusted itself so as to correspond to this real situation.”[14]
If one reinterprets the meaning of “real,” for example by bringing it closer to “potentiality,” then certain versions of quantum mechanics can also be realist. In any case, if one remains forever tied to the common-sense notion of “real,” it will be difficult to make “realism” into a philosophical position that is still reasonable and forceful in the contemporary era after quantum mechanics.
January 10, 2009
[1] Nicholas Bunnin and Yu Jiyuan, eds., *A Dictionary of Western Philosophy: English-Chinese Comparative Edition*, People’s Publishing House, 2001, p. 902
[2] Michael Devitt, “REALISM/ANTI-REALISM,” materials, p. 14
[3] Alexander Bird, *The Philosophy of Science*, trans. Jia Yulin and Rong Xiaoxue, China Renmin University Press, 2008, p. 121
[4] Michael Devitt, “REALISM/ANTI-REALISM,” materials, p. 14
[5] Cited in Nicholas Bunnin and Yu Jiyuan, eds., *A Dictionary of Western Philosophy: English-Chinese Comparative Edition*, People’s Publishing House, 2001, p. 650 (Chinese translation adjusted)
[6] There is another remarkable feature of “electrons” worth mentioning: any two electrons are “exactly the same,” or rather, “indistinguishable.” Of course, we can distinguish the electron in this laboratory from the electron in that laboratory, but this is actually only a distinction of spatiotemporal position; once any two electrons are brought together, they are identical. Add to this the uncertainty principle of quantum mechanics, and you simply cannot say that the electron fired from the electron gun and the electron that subsequently strikes the screen are “the same one,” because due to quantum fluctuations, this electron may have undergone countless annihilations and rebirths during its “journey”… So, in a certain sense, “electron” is not a “universal”; nor is it something abstracted from countless individual particulars. According to Leibniz’s principle of identity, one should say that there is only one electron in the universe—although there are no two leaves exactly alike, there are no two electrons differing even in the slightest! (According to Feynman’s conception, all electrons can be understood as one electron darting back and forth through spacetime.) In this way, the “universals realism” concerning “electron” faces serious problems. Of course, the question of realism in the sense of universals and particulars is not the theme of this article. Moreover, if one accepts that “electron” is not a real entity but a constructed theoretical tool, this problem is easily resolved as well.
[7] Related knowledge ought to be basic common sense in the philosophy of science community, so I will not narrate it in too much detail in the main text. But in order to show that I do indeed understand the relevant background knowledge, I place here my own (ready-made) brief introduction to the double-slit experiment:
The double-slit interference experiment is a simple experiment encountered already in middle-school physics. It reveals the wave nature of light: if a beam of light is sent through two parallel slits placed side by side, and a screen is properly positioned behind the slits, one can observe interference fringes of alternating light and dark. The dark fringes are caused precisely by the cancellation of the peaks and troughs of the coherent waves from the two slits. If a beam of electrons is used, interference fringes can also be observed, proving that electrons are waves too. Yet we also know that energy is discontinuous, that light is composed of countless tiny, indivisible “photons,” and that electrons are of course the same. Then what if we emit only one particle at a time? If it passes through the double slit, it can leave a tiny dot on the screen, which displays its particle nature. The following idea seems obvious: if a particle passes through the double slit and reaches the screen, then it “either passed through slit A or passed through slit B.” Just as a particle can leave only one dot on the screen, it cannot possibly pass through both slits at once! Then shouldn’t the effect of releasing 100 particles one by one onto the screen be equivalent to first closing slit A and letting 50 particles pass through slit B, then closing slit B and letting 50 particles pass through slit A? The above analysis seems logically sound. However, the fact is this: although one particle striking the screen is merely one dot, enough dots on the same screen will reveal an overall pattern. The experimental result is that if the double slit is kept open throughout, and enough particles are allowed to pass through one by one, the final pattern formed on the screen is still interference fringes! We know that interference fringes are a wave phenomenon, the result of waves passing through both slits simultaneously and interfering with each other. But how does a single particle passing through the double slit produce interference? Is it interfering with itself? Can one particle pass through both slits at once?
However, if we try to check how the particles pass through the double slit, for example by placing a detector on one of the slits, the result remains: the particle “either passed through slit A or passed through slit B.” But once this observation is made, the final pattern on the screen can no longer be interference fringes; it turns into a simple superposition, namely “first closing slit A and letting 50 particles pass through slit B, then closing slit B and letting 50 particles pass through slit A”! What may be even more puzzling is that an improved experiment—for example, replacing the double slit with a half-silvered mirror—the so-called “delayed-choice experiment”—can postpone the decision of whether or not to perform the observation in midcourse until after the particle has already passed through the double slit! In other words: whether or not an interference phenomenon eventually occurs—that is, “how the particle passed through the double slit”—can be postponed until after the particle has actually passed through the double slit, and then decided by the experimenter!
[8] W. Heisenberg, *Physics and Philosophy*, trans. Fan Dainian, Commercial Press, 1984, p. 81
[9] Since the EPR paradox has indeed been experimentally confirmed, and for other reasons as well, it is becoming increasingly difficult to provide a realist explanation of quantum phenomena. Even Bohm’s interpretation, while preserving the individuality and independence of theoretical objects, or the principle of bivalence, still presents a picture of reality that is counterintuitive and contrary to everyday experience. Things like the “implicate order” may not be any less absurd than the Copenhagen interpretation. Any effort to understand contemporary science with common-sense ideas of reality is probably doomed to fail.
[10] Cited in Roger G. Newton, *What Is Scientific Truth?*, trans. Wu Jike, Shanghai Science and Technology Education Press, 2001, p. 179
[11] W. Heisenberg, *Physics and Philosophy*, trans. Fan Dainian, Commercial Press, 1984, pp. 109–110
[12] Ibid., p. 22
[13] Ibid., pp. 21–22
[14] Ibid., p. 119
Heisenberg goes on to say: “But this is not the kind of exact language in which one can use ordinary logical forms; rather, it is the kind of language that evokes images in our minds.” Later, Heisenberg also mentions that “in classical logic, the relations between different levels of language are one-to-one. The two statements ‘the atom is in the left half’ and ‘it is true that the atom is in the left half’ belong logically to different levels. In classical logic, these two statements are completely equivalent; that is to say, they are either both true or both false; it is impossible for one to be true while the other is false. But in the logical form of complementarity, this relation is more complicated. The correctness or incorrectness of the first statement still includes the correctness or incorrectness of the second. But the incorrectness of the second statement does not include the incorrectness of the first. If the second statement is incorrect, that may be because one cannot determine whether the atom is on the left: the atom need not necessarily be on the right.”
——We note that the “classical logic” that Heisenberg points to as inapplicable in quantum mechanics does not necessarily compel us to abandon a precise logic. We find that, even without considering the feeble “quantum logic,” intuitionistic logic does not fail here; by restricting the law of excluded middle, intuitionistic logic can provide the same exact explanation without falling into paradox.
Postscript: The assignment I originally intended to write was mainly about how intuitionism explains quantum paradoxes. As it turned out, just the introduction already ran to more than three thousand characters, so I’ll have to leave the rest for later. The main question in the original plan was also in what sense intuitionism or quantum mechanics are each “anti-realist.” In any case, the definition of the topic of realism is something one cannot get around.
Latest Comments
- Xingkong 2009-01-12 22:27:31 Anonymous 124.205.78.225 Is this Sun Laoshi’s paper? Or Wu Laoshi’s paper?
I can’t understand the article at all; it’s pure fluff, just adding a bit of popularity - Gǔchǔ2009-01-12 22:52:10 Of course it’s Sun Laoshi’s paper. Wu Laoshi’s is still in the works; progress is fairly smooth, but the result definitely still won’t satisfy me…
Translated from the Chinese original with AI assistance. The original text is authoritative.
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