What is the nature of change in scientific theories? Is it reasonable to consider science as a journey from ignorance to truth? Or is there a mythology of science that distorts the nature of the scientific endeavour?
When I first went to university, it was to study astrophysics. I was enthusiastic about the subject, and eager to learn. My expectation to some degree was that the workings of the universe were going to be explicated to me, and that I was going to be shown experiments which underpinned the theories of nature that had been developed, and from which those theories could be derived. But in fact, the theories were taught as strictly factual, and only then were the experiments enacted. Students, having already learned the prevailing models of reality, approached each experiment with the certain knowledge of the expected results.
When we were asked, for instance, to take measurements from which to calculate the gravitational constant of the universe, there was no doubt as to what the correct answer was expected to be. In practice, few if any students produced results that would yield an answer sufficiently close to that dictated by prior theory. In the face of conflicting experimental evidence, most students would attempt the experiment again, usually once again yielding results which were not of the kind expected. After a few failed attempts, many students then adjusted their data in order to more closely resemble the expected results of the experiment.
This experience greatly challenged my expectations of science. It was not that the theory in question was fundamentally in error – if we had, for instance, averaged all the data gathered in the lab by all the students, the mean result would almost certainly have resembled the expected results. But what I observed in the physics laboratory was students of science faced with unexpected data and then, instead of reporting this honestly as my preconceptions of the scientific method demanded, changing their measurements to conform with the expected results. That this was the way to get the highest marks from the laboratory experiments is not in doubt, but if the central value of science is truth, the students were not learning this value – they were learning how to toe the line with existing theory.
Scientists, in general, are not taught philosophy of science, and as a result rarely question their abstract beliefs about the nature of the scientific process. As a result, science has developed a persistent mythology, central to which is the idea that science uncovers the truth, and as the theories and techniques of science develop, science moves closer and closer to absolute truth.
The celebrated historian and philosopher of science Thomas Kuhn, in his seminal work The Structure of Scientific Revolutions (first published in 1962) put forward one of the decisive criticisms of this view. He observed, from study of the development of European science, that scientists’ commitment to particular theoretical frameworks acted as a barrier to seeing data in a different light – even when that data was entirely contradictory to the theory. Like the students in the physics lab I encountered, theory was considered to trump observation to some degree.
Kuhn’s historical analysis resulted in a model of science that denied the conventional belief in science as a process of accretion. The idea that science gradually assimilated building blocks and advanced in steady and discrete steps did not match up to the historical record. Instead, Kuhn saw periods of what he termed normal science, during which scientists worked to adapt their current theories to a range of experimental observations, and periods of scientific revolution – when the old theories came into crisis, and were eventually supplanted by new theories.
The view of scientific fields proposed by Kuhn was that a particular field does not emerge within science until scientists working in this area begin to develop a common framework. Kuhn terms this framework a paradigm, a term he uses ambiguously in a number of subtly different contexts. On the one hand, a paradigm describes the collection of symbolic generalisations, experimental methods and common assumptions shared by practitioners of a given scientific field. On the other, paradigms represent specific exemplars of scientific puzzle solving, including both experimental and theoretical results to problems. We can see a paradigm as a set of common beliefs that a group of scientists share. Despite the intense faith that is placed in science, these beliefs do not necessarily correspond to reality – rather, they provide a framework that enables the scientists to investigate reality in a particular way.
Kuhn suggests that during periods of normal science, scientists are mostly attempting to “force nature into the preformed and relatively inflexible box that the paradigm supplies.” No paradigm explains all the facts with which it can be confronted, and the general process of science therefore works on the solutions to puzzles – problems in adapting the theoretical models of that paradigm to the description of reality. This commitment to a particular paradigm is essential to the scientific process in Kuhn’s opinion. Normal science is only able to proceed on the predicate that scientists know “what the world is like.”
Anomalous data – that which cannot be made to fit into the box provided by the paradigm – is usually ignored, or interpreted in a manner consistent with the paradigm’s assumptions, or else the theoretical framework of the paradigm is adjusted to compensate for the discrepancy. Experienced scientists, having had great success with their paradigm, are unwilling to abandon it in the light of contradictory evidence. This can be seen as a necessary commitment, because to give up a particular paradigm without adopting a new one would be to abandon science entirely: there can be no science without a particular model by which the investigatory process can proceed.
Kuhn observes that new paradigms gradually replace old ones as a result of a growing view (usually among newcomers to the field, since these are least committed to the old beliefs) that the old methods are no longer able to guide the exploration of a particular area in which the old paradigm used to lead the way. But the transition between paradigms does not often proceed without difficulties – the commitment to the old paradigm remains strong, and it is hard for rational discussion to take place between two individuals who are using different paradigms.
Often, the elder scientists are unwilling or unable to abandon the paradigm which has lead to such success and progress during their time, and this is only natural. As Max Planck observed: “a new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.”
There is no objective means of resolving these disputes between competing explanations. Scientists must necessarily premise their own paradigm in order to argue in its favour, a circular process that can nonetheless be quite persuasive. Although arguments are usually couched in terms of the capacity of the competing theories to explain experimental facts, it is not generally possible to determine which is the better theory by comparison with facts. All significant scientific theories fit the facts to some extent. But when two theories are competing with each other, the issue is not how much each theory fits the facts, per se, but rather whether or not one theory fits the facts better than another.
Even this may not be the means in which the commitment to a paradigm is changed. What is being asked for is a fundamental alteration to the way a particular scientific field is practiced, and for this argument to be persuasive what must be offered is something more than correspondence to facts – as already mentioned, most scientific theories can be made to adequately explain the facts they are faced with. For example, chemists abandoned phlogiston theory, but at the time that the theory of combustion in the presence of oxygen was forming, phlogiston adequately explained the majority of the observed facts. Many of these facts presumed phlogiston in their formulation. But the new idea carried with it the promise of future progress, and it was faith in this possibility that helped drive this paradigm change forward.
The model of reality suggested by one paradigm generally
involves quite different entities to its rival. Consider the view of the world
Part of the mythology of science is to see changes like these (from an old successful theory to a new one) both as progressing towards truth, and also to view the old theory not as having been disproved but as a special case of the new theory. This tendency is particularly prevalent in relation to the paradigm shift from Newtonian to Einsteinian physics, and scientists can indeed demonstrate how the Newtonian equations can be derived from the later theories. But this process is misleading. An abandoned theory can always be viewed as a special case of its successor, but to do so one must transform the original theory in the terms of the new one – and this is something that can only be done in hindsight.
This rewriting of history is endemic to science. The scientists of earlier ages are represented in textbooks and the like as having worked on the same set of problems, and in accordance with the same guidelines, as modern science. This makes science appear to be cumulative, but it is a fiction created by ignoring the crises that accompany scientific revolution. Earlier scientists worked on very different problems, because their models of the world lead them to different puzzles to solve. Because the results of scientific research do not seem to depend upon the history of their development (that is, scientific theories do not depend upon their historical origins for their veracity) it seems acceptable to abstract over the details of their development. In doing so, the nature of the scientific endeavour becomes distorted to appear both linear and cumulative.
Furthermore, this view distorts the nature of the abandoned paradigms. There is a tendency to look at certain discarded theories as myths that have been disproved – but this perspective will not stand up to scrutiny. The old paradigms were derived through the same essential scientific process as the new paradigms, and from a historical perspective both the old and the new must be seen as scientific – else all scientific knowledge can be accused of being a myth. It is not that the old beliefs were false and the new ones true – for a future paradigm shift may well render the current ideas false by this reasoning. Rather, the science of the past contains views and beliefs wholly incompatible with the models of present scientists, yet all such paradigms are still by their very nature scientific. They proceeded from fact and measurement, with the goal of providing explanations of these facts.
Kuhn challenges our preconceptions of science as evolving towards objective truth, and instead suggests we should understand scientific progress as evolution from the community’s prior state of knowledge. There is no perfect conception of reality that science is travelling towards; there is no ideal goal state that science will ultimately evolve into. Such ideas are anachronistic fallacies that do not match up with the history of science.
The idea of goal-directed progress was abandoned in the
Ultimately, scientific knowledge is, like language, an intrinsic property of a group of people. To understand that knowledge, it is necessary to understand the nature and characteristics of the groups that create and use this knowledge. Science is the name we give to the practices of scientists, who by dedication to an empirical view of the world gradually refine their ideas, and produce exceptional instruments which in turn allow for the creation of new technologies. Later scientific theories show progress – they are better at solving puzzles in often very different environments to those of their predecessors – but it is a mythological view of science that sees science as truth, or evolving towards truth. Science evolves as scientists refine their perspectives, but this refinement is an adaptation to new conditions of knowledge, and not an inevitable march towards perfection.
The opening image is Dancing Light, a refraction caustic by Alan Jaras which I found here. As ever, no copyright infringement is intended and I will take the image down if asked.