Hasok Chang sees a new role for the history and philosophy of science

What is the use of philosophy? That is a challenging question to answer in the modern intellectual landscape dominated by empirical science. There is a common impression that philosophers just sit around and engage in idle talk, while scientists make real investigations and deliver results that are useful as well as truthful. Even professional philosophers feel the pressure of the success of science and often respond with a subservient naturalism, which would reduce philosophy of mind to neurophysiology, epistemology to cognitive psychology, and metaphysics to the latest fashion in physics. A completion of such a naturalist project would be the end of philosophy as we know it; if philosophy’s subject matter is really science, then it would be best to leave it to scientists. It is absurd conceit to think that we philosophers can “think” better than anyone, so that we can step in and draw some wise conclusions from the scientific material, which scientists themselves are missing because they are sloppy or limited in their thinking.

I wish to resist this self-denigrating naturalism in philosophy, fashionable as it is these days. The relation between philosophy and science needs to be seen in a new light. A look back at the long-term history of scholarship will help us re-orientate ourselves here. There was a time when nearly all academic inquiry was called “philosophy”. But various scientific disciplines (and other practices such as law and medicine) gradually carved themselves out and left the realm of philosophy. After the departure of astronomy, mechanics, experimental physics, chemistry, geology, biology, psychology, anthropology, sociology, economics, and so on, what is left in philosophy proper seems an empty shell. Our current academic discipline called “philosophy” became restricted and defined, as it were, against its own will.

This history goes some way to explain the origin of the common notion that philosophy should deal with “deep” questions, that its discourse has to be general, abstract and systematic. This is a reaction against all the specialisms declaring their independence from philosophy. The defining feature of what remains as philosophy must be that it is not specialist but general, aspiring to universality. Transcending the vagaries of specialist disciplines also means dealing with questions that are immutable, as we go on a quest for an eternal truth.

In articulating my own conception of philosophy, I want to propose a different contrast, a different way of being counter-specialist. Philosophical questions are not deeper than scientific questions, only different. Here I take a clue from Thomas Kuhn’s philosophy of science, though perhaps not in a way that he would have envisaged himself. In Kuhnian terms, science does not emerge from “pre-science” until the field of legitimate questions gets narrowed down with clearly recognized boundaries. Historically this was a slow and gradual process. For a long time it was common for one and the same treatise to contain tangled discussions of metaphysics, methodology, and what we would now identify as the proper “content” of science. Philosophy once aspired to encompass all knowledge, but what is now left under the rubric of philosophy is not the all-encompassing scholarship it once was. Philosophy as practised now does not and cannot include science. But in my view that is just where its most important function now lies: to address what science and other specialisms neglect.

The classic clash between Kuhn and Karl Popper from the 1960s illustrates an important aspect of my proposal. To Popper’s insistence that criticism was “the lifeblood of all rational thought”, Kuhn retorted: “To turn Sir Karl’s view on its head, it is precisely the abandonment of critical discourse that marks the transition to a science.” In return, Popper declared that Kuhnian normal science, in which serious questioning of the ruling paradigm was discouraged, was “a danger to science and, indeed, to our civilization.” In my own life, I began on Popper’s side of this debate: as an undergraduate student studying physics, I was always dissatisfied with the unquestioning attitude that I was expected to take about the fundamentals of physics. My professors, who were mostly “normal” scientists, often answered my questions with a killer non-answer: “It’s a philosophical question.” I went on to do a PhD in philosophy, almost out of spite, full of regret about the state of physics. Over the years, however, I came to recognize that Kuhn had a point about how science required a narrow focus. Yet society needs the critical attitude. The solution to the Popper–Kuhn dilemma is to leave normal science alone, but to practise philosophy of science alongside it, as a complement. So I came to see philosophy of science as a continuation of science by other means (to paraphrase Clausewitz).

Complementary science
Let me now express my position more clearly and systemically: philosophy of science can seek to generate scientific knowledge in places where science itself fails to do so; I call this the complementary function of philosophy of science, as opposed to its descriptive and prescriptive functions. I propose taking the philosophy of science as a field which investigates scientific questions that are not addressed in current specialist science — questions that could be addressed by scientists, but are excluded due to the necessities of specialization.

A need for philosophy of science in the complementary mode, or complementary science as I will call it, arises from the fact that specialist science cannot afford to be completely open. (I speak of “specialist science” rather than “normal science”, so as not to distract those who reject Kuhn’s particular ideas about normal science or paradigms.) There are two aspects to this necessary lack of openness. First, in specialist science many elements of knowledge must be taken for granted, since they are used as foundations or tools for studying other things. This also means that certain ideas and questions must be suppressed if they are heterodox enough to contradict or destabilize the taken-for-granted items of knowledge. Such are the necessities of specialist science, quite different from a gratuitous suppression of dissent. Second, not all worthwhile questions can be addressed in specialist science, simply because there are limits to the number of questions that a given community can afford to deal with at a given time. Each specialist scientific community will have some degree of consensus about which problems are most urgent, and also which problems can most plausibly be solved. Those problems that are considered either unimportant or unsolvable will be neglected. All this is not malicious or misguided neglect, but a reasonable act of prioritization necessitated by limitations of material and intellectual resources.

All the same, we must face up to the fact that suppressed and neglected questions represent a loss of knowledge, actual and potential. The complementary function of philosophy of science is to recover and even create such questions and, hopefully, some answers to them as well. Therefore the desired result of research in philosophy of science in this mode is an enhancement of our knowledge and understanding of nature.

The character of knowledge generated by complementary science
I have claimed that complementary science can generate scientific knowledge where science itself fails to do so. On the face of it, this sounds absurd. How could any knowledge about nature be generated by philosophical studies? And if complementary science does generate scientific knowledge, shouldn’t it just be counted as part of science, and isn’t it foolhardy to suggest that such scientific activity could be undertaken by anyone but properly trained specialists? Such a sense of absurdity is understandable, but I believe it can be dispelled through a more careful consideration of what it means to generate knowledge. As I have indicated already, there are three main ways in which complementary science can add to scientific knowledge.

Critical awareness
Superficially, it might appear that critical philosophical scrutiny would undermine scientific knowledge, because it tends to generate various degrees of doubt about the accepted truths of science. Generating doubt may seem like the precise opposite of generating knowledge, but I would argue that constructive skepticism can enhance the quality of knowledge. If something is actually uncertain, our knowledge is superior if it is accompanied by an appropriate degree of doubt rather than blind faith. If the reasons we have for a certain belief are inconclusive, being aware of the inconclusiveness prepares us better for the possibility that other reasons may emerge to overturn our belief. In practice it is going to be very difficult for specialists to maintain this kind of critical vigilance on the foundations of their own practice, except in isolated cases. The task is much more easily and naturally undertaken by philosophers of science.

Even philosophers tend not to recognize critical awareness and its productive consequences as contributions to scientific knowledge. Thereby philosophy undersells itself. There is a sense in which we do not truly know anything unless we know how we know it, and on reflection few people would deny that our knowledge is superior when we are also aware of the arguments for and against our beliefs. That is not incompatible with the fact that such superior knowledge can constitute a hindrance in the achievement of certain aims that require an effective non-questioning application of knowledge.

For example, there is little that deserves the name of knowledge in being able to recite that the earth revolves around the sun. The belief carries more intellectual value if it is accompanied by the understanding of the evidence and the arguments that convinced Copernicus and his followers to reject the firmly established, highly developed and eminently sensible system of geocentric astronomy established by Ptolemy, as detailed by Kuhn in his first book, The Copernican Revolution (1957). This is exactly the kind of scientific knowledge that is not easily available in current specialist science but can be given by philosophy of science. And examples such as this also illuminate the point that philosophy of science in its complementary mode is crucially aided by history of science. There are many other cases in which work in history-and-philosophy of science has raised and examined very legitimate questions about how certain scientific controversies were settled. In the thriving tradition in the philosophy of modern physics, for instance, a community of philosophers have been questioning and re-examining the orthodox formulations and interpretation of various theories, especially quantum mechanics.

Critical awareness is something I have tried to achieve in my own work, including the philosophical history of temperature contained in Inventing Temperature (2004). Scientists found it impossible to reach a conclusive positive solution to the problem of choosing the correct thermometric fluid, though Regnault’s comparability criterion was effective in ruling out most alternatives except for a few simple gases. The extension of the thermometric scale to the realms of the very hot and the very cold suffered from similar problems, and scientists forged ahead without being able to say conclusively which of the competing standards were correct. That is how matters stood at least until Kelvin’s concept of absolute temperature was operationalized in the late 19th century. But it was a futile hope that a highly theoretical concept of temperature would eliminate the inconclusiveness of measurement, since the problem of judging the correctness of operationalization was never solved completely, though the iterative solution adopted by the end of the 19th century was admirable. I would submit that after a critical assessment of scientific work in order to solve all these problems, our scientific knowledge of the meaning and measurement of temperature is immeasurably improved.

Recovery
Once critical awareness about science is reached, history of science takes on an entirely different kind of significance. History can teach us about nature through the recovery of forgotten scientific knowledge. The potential for such recovery is shown, again, in my recent work on temperature, which begins with a question about how the so-called “fixed points” of thermometers can be demonstrated to be fixed, in the absence of points that are previously agreed to be fixed. This question led me to discover a significant debate about the fixedness of the boiling point in the 18th and the 19th centuries. Many investigators starting from Jean-André De Luc in the late 18th century knew that pure water did not always boil at the “boiling point” even under standard pressure. They built up a growing and sophisticated body of knowledge about the “superheating” of water and other liquids that took place under various circumstances (and at least in one case observed that boiling could also take place slightly under the boiling point as well). But by the end of the 19th century we witness John Aitken’s complaint that authoritative texts were neglecting this body of knowledge, either through ignorance or through oversimplification. Personally, I can say that I have received a fair amount of higher education in physics at reputable institutions, but I do not recall ever learning about the superheating of water and the threat it might pose to the fixity of the boiling point. All I know about it has been learned from reading papers and textbooks from the 18th and 19th centuries.

This is not to say that knowledge of superheating has been lost entirely to modern science. The relevant specialists do know that liquid water can reach temperatures beyond the normal boiling point without boiling, and standard textbooks of physical chemistry often mention that fact briefly. Much less commonly noted is the old observation that water that is actually boiling can have various temperatures deviating from the standard boiling point, which seems to be discussed only by engineers concerned about heat transfer. There are vast numbers of scientifically educated people today who do not know anything about these very basic and important phenomena. In fact, what they do claim to know is that superheating does not happen, when they unsuspectingly recite from their textbooks that pure water always boils at 100°C under standard atmospheric pressure. Most science students are not taught about superheating because they do not need to know about it, unlike heat-transfer engineers.

There is another category of experimental knowledge that tends to get lost, namely facts that actively disturb our basic conceptual schemes. The best example of this category that I know is Marc-Auguste Pictet’s experiment from the late 18th century, in which there was an apparent radiation and reflection of rays of cold, as well as rays of heat. This experiment received a good deal of attention at the time, but gradually it became forgotten. Nowadays only the most knowledgeable historians of that period of physics seem to know about this experiment at all. Unlike superheating, the radiation of cold is not a phenomenon recognized by most modern specialists on heat and radiation, to the best of my knowledge. It just does not fit into a scheme in which heat is a form of energy and cold can only be a relative deficit of energy, not something positive; remembering the existence of cold radiation will only create cognitive dissonance for the energy-based specialist.

The recovery of forgotten knowledge is not restricted to facts, but extends to ideas as well (and it is, after all, very difficult to separate facts and ideas cleanly). In fact, historians of science for many decades have made great efforts to remember all sorts of ideas that have been forgotten by modern science. This kind of recovery is the mainstay of the history of science, so much so that there is no point in picking out a few examples out of the great multitude. But in order for the recovered ideas to enter the realm of complementary science, we need to get beyond thinking that they are merely curious notions from the past that are either plainly incorrect or no longer relevant.

The consideration of recovery raises a basic question about what it means for knowledge to exist. When we say we have knowledge, it must mean that we have knowledge; it is no use if the ultimate truth about the universe was known by a clan of people who died off 500 years ago without leaving any records, or by some space aliens unknown to us. Conversely, in a very real sense, we create knowledge when we give it to more people. And the acquisition of the “same” piece of knowledge by every new person will have a distinct meaning and import within that individual’s system of beliefs. When it comes to knowledge, dissemination is a genuine form of creation, and recovery from the historical record is a form of dissemination — from the past to the present, across a gap created by institutional amnesia, bridged by the durability of paper, ink and libraries.

New developments
Recovery and critical awareness are valuable in themselves, but they can also stimulate the production of genuinely novel knowledge. Historians have generally shrunk from further developing the systems of knowledge that they uncover from the past record of science. An emblematic example is Kuhn. Having made such strenuous and persuasive arguments that certain discarded systems of knowledge (e.g. Aristotelian physics, Ptolemaic astronomy or the phlogiston theory) were coherent and not simply incorrect, Kuhn gave no explicit indication that these theories deserved to be developed further. Why not? According to his own criterion of judgement, scientific revolutions constitute progress when the newer paradigm acquires a greater problem-solving ability than ever achieved by the older paradigm. But how do we know that the discrepancy in problem-solving ability is not merely a result of the fact that scientists abandoned the older paradigm and gave up the effort to improve its problem-solving ability? A similar question also arises at the conclusion of some other historians’ works on scientific controversy. For example, Steven Shapin and Simon Schaffer, in their Leviathan and the Air-Pump (1985), strongly challenged the received wisdom that Thomas Hobbes’s ideas about pneumatics were rightly rejected in favor of the superior knowledge advanced by Robert Boyle. But they gave no indication that it would be worthwhile to try developing Hobbes’s ideas further.

The historian, of course, has an easy answer here: it is not the job of the historian to develop scientific ideas actively. But whose job is it? Philosophers have no easy excuse here. It is perfectly understandable that current specialist scientists would not want to be drawn into developing research programs that have been rejected long ago, because from their point of view those old research programs are, quite simply, wrong. This is where complementary science enters. Lacking the obligation to conform to the current orthodoxy, the complementary scientist is free to invest some time and energy in developing unorthodox systems.

One clear step is to extend the experimental knowledge that has been recovered. We can go beyond simply reproducing curious past experiments. Historians of science have tended to put an emphasis on replicating the conditions of the historical experiments as closely as possible. That serves the purpose of historiography, but does not necessarily serve the purpose of complementary science. In complementary science, if a curious experiment has been recovered from the past, the natural next step is to build on it. This can be done by performing better versions of it using up-to-date technology and the best available materials, and by thinking up variations on the old experiments that would not only confirm but extend the old empirical knowledge.

Less demanding of resources but mentally more daring would be new theoretical developments. The realm of theoretical development is where the complementary scientist is likely to face the greatest degree of objection or incomprehension. If an idea proposed in complementary science does not conform to the currently orthodox view of the directions in which productive new developments are likely to come, specialists will dismiss it out of hand as wrong, implausible, or worthless in some unspecified way. On the other hand, if the idea is deemed worthwhile by the specialists, it will be declared as part of science itself. But the complementary scientist is neither a crank nor an undereducated specialist. What distinguishes the complementary scientist from the crank scientist is that complementary science is inherently a pluralistic enterprise. When the complementary scientist picks up a rejected research program to explore its further potential, or suggests a novel research program, that is not done with the crank’s conviction that his particular heresy represents the only truth.

The use of philosophy
Having spelled out the notion of philosophy as complementary science, I would like to return to the question I posed at the beginning: what is the use of philosophy? There is one common impression of philosophy that hits the nail on its head: it is impractical. We tend to call something a “philosophical” question if it is something that we do not normally need to deal with in the course of routine action. There are various reasons why relevant questions may be excluded from a system of thought or practices. The questions may be too general; they may threaten some basic beliefs within the system; asking them may be pointless because every specialist knows and agrees on the correct answers; the answers may not make any significant practical difference; and so on. And in the end, questioning has to be selective because it is simply impossible to ask the infinity of all possible questions. But philosophy can function as the embodiment of the ideal of openness, or at least a reluctance to place restrictions on the range of valid questions. Professional philosophy exists so that questions, and our capacity to ask questions, are preserved for society. These questions may come to be relevant one day. Philosophy of science exists so that scientific knowledge can be preserved and developed in a broad sense that goes beyond the current paradigms.

Is philosophy as I conceive it a normative enterprise in relation to the practices of life that it considers? More specifically, is philosophy of science normative in relation to science? Is complementary science normative in relation to orthodox specialist science? These are difficult questions to answer unequivocally, and I think the subtlety of the issue can be captured as follows: complementary science is critical but not prescriptive in relation to specialist science.

There are two different dimensions to the critical stance that complementary science can take toward specialist science. First, when complementary science identifies scientific questions that are excluded by specialist science, it is difficult to avoid the implication that we would like to have those questions answered. That is already a value judgment on science, namely that it does not address certain questions we consider important or interesting. However, at least in a large number of cases, this judgment also comes with the mitigating recognition that there are good reasons for specialist science to neglect those questions. That recognition prevents the step from judgment to prescription. The primary aim of complementary science is not to tell specialist science what to do, but to do what specialist science is presently unable to do. It is a shadow discipline, whose boundaries change exactly so as to encompass whatever gets excluded in specialist science.

The second dimension of the critical stance is more controversial. On examining certain discarded elements of past science, we may reach a judgement that their rejection was either for imperfect reasons or for reasons that are no longer valid. Such a judgement would activate the most creative aspect of complementary science. If we decide that there are avenues of knowledge that were closed off for inadequate reasons, then we can try exploring them again. At that point complementary science would start creating parallel traditions of scientific research that diverge from the dominant traditions that have developed in specialist science. It is important to note that even such a step falls short of a repudiation of current specialist science. Since we do not know in advance whether and to what degree the complementary traditions might be successful, the act of creating them does not imply any presumption that it will lead to superior results to what the specialists have achieved since closing off the avenues that we seek to re-open.

Complementary science could trigger a decisive transformation in the nature of our scientific knowledge. Alongside the expanding and diversifying store of current specialist knowledge, we can create a growing complementary body of knowledge that combines a reclamation of past science, a renewed judgment on past and present science, and an exploration of alternatives. This knowledge would by its nature tend to be accessible to non-specialists. It would also be helpful or at least interesting to the current specialists, as it would show them the reasons behind the acceptance of fundamental items of scientific knowledge. It may interfere with their work in so far as it erodes blind faith in the fundamentals, but I believe that would actually be a beneficial effect overall. The most curious and exciting effect of all may be on education. Complementary science could become a mainstay of science education, serving the needs of general education as well as preparation for specialist training. That would be a most far-reaching step, enabling the educated public to participate once again in building the knowledge of our universe.

Hasok Chang is reader in philosophy of science at University College London. His first book, Inventing Temperature: Measurement and Scientific Progress was a joint winner of the 2006 Lakatos Award. He was also short-listed for a Times Higher Education Young Academic Author of the Year award.