Jouni-Matti Kuukkanen, blog, Thomas Kuhn

Jouni-Matti Kuukkanen´s letter to Thomas Kuhn: "Did you really mean to argue that science is not a rational activity?"

Dear Thomas Kuhn,

I am writing this letter to you from a place and a country that, as far as I know, you never visited. And let me tell you, there is a lot here that you could do!

When I consider your career from my own perspective and from that of the times I live in, I am struck by three things about you: your multidisciplinary approach, the impact you had on our culture, and the way you historicized our conception of science. Your multidisciplinarity is captured well in how you described yourself. As you took up teaching a course centred around cases studies in the history of science at Harvard University in the early 1950s, the “physicist became a historian for philosophical purposes”[i].  In a rare feat, you mastered three disciplines. When discussing your cultural impact, it is not even necessary to highlight the way in which you and a few of your contemporaries succeeded in giving a birth to a new academic discipline: intergrated history and philosophy of science.[ii] For a more telling metric for evaluating the significance of your contributions, we need only look at how many of the concepts you introduced in your book The Structure of Scientific Revolutions[iii] have since made their way into journalistic and everyday language. These include “paradigm”, “scientific revolution”, and “incommensurability”.

In large part thanks to you, our conception of science was historicized. And this, in the end, emerges as your most important achievement. You succeeded in pointing out that an idealized view of science – whether focused on the scientific method, the concept of rationality, progress, or explanatory models – cannot stand up to historical scrutiny. Science is, at its core, a dynamic process. Or perhaps we could express this idea by pointing out that science is essentially historical, and therefore changeable.

It seems to me that ever since science became historicized, we have been moving back towards an approach that eschews the lens of history. Scientific evolution and the dynamism of science spark less interest than the supposed timelessness of the scientific worldview as true and absolute. It is in light of this observation that I pointed above to the work to be done here, in Oulu, in Finland, and beyond. In The Structure of Scientific Revolutions, you begin with the following words:

“History, if viewed as a repository for more than anecdote or chronology, could produce a decisive transformation in the image of science by which we are now possessed. That image has previously been drawn, even by scientists themselves, mainly from the study of finished scientific achievements as these are recorded in the classics and, more recently, in the textbooks from which each new scientific generation learns to practice its trade.”[iv]

How much, we may ask, have matters actually changed since? In Finland and elsewhere, only a decidedly minor role is afforded to teaching the history of science across subject lines or even within specific disciplines.  In this country, little has been done to advance the teaching of the history –  let alone the integrated history and philosophy –  of science. Against this regrettable backdrop, it brings me great joy to say that the University of Oulu is the only Finnish institution that offers the history of science (and ideas) as a major subject, with increasing attention given to the teaching of philosophy as well. If we truly wish to understand science as an evolving historical phenomenon, however, we still have a long way to go.

At this point, one may wonder about the point and utility of a historical perspective, but these could be found in unexpected places. For example, the historian and philosopher of science Hasok Chang from the University of Cambridge has written[v] about unrealized trajectories of science that could have contributed to science in the past, and even enrich contemporary science now. He has introduced the concept of complementary science, which entails that the history and philosophy of science can be continuation of science by other means. In this context, Chang demonstrates that contingencies are an ever-present factor in science, as there are always possible paths of scientific inquiry that, despite their soundness, are left untaken. Among other things, Chang's nuanced analysis reveals that the rejection in the 18th century of the famous phlogiston theory that sought to explain the processes of combustion and the formation of water in favour of Antoine Lavoisier's oxygen theory was not inevitable. In fact, pursuing the work on phlogiston chemistry could have proven extremely fruitful and led to the development of the modern concepts of energy and the electron much earlier.[vi] 

Even in light of the above, a historical and dynamic perspective on science is first and foremost an exciting driver of critical thinking and an indispensable tool for those who wish to understand the true nature of science. Prior to the professionalization of the field, history of science was generally written either by philosophers or the scientists themselves, and often took on a lofty and laudatory tone. Let us consider, for instance, the view taken by Alexandre Koyré, Russian-born French philosopher, who understood science as a manifestation of pure rationality, or George Sarton, Belgian-born American chemist and one of the founding fathers of the history of science, who saw science as a demonstration of humanity's greatness.

Or we may turn to the positivist conception of science, which sees it as a constant accumulation of facts, which, in turn, give rise to scientific theories and laws. You, along with other historical philosophers of science, called into question such assumptions about the nature of science. Can we ascribe to science an immutable nature, such as the scientific method or explanation? How does science appear to us when we take account of the changes it undergoes? And what do scientists actually do? By subjecting our view of science to historical scrutiny, you started pursuing the science of science, or, in other words, systematically and empirically (which also implies historically) examining scientific practices.

The great debates of your time on the rationality of science have never ceased to serve as a source of inspiration to me. And while many positive academic and societal developments have taken place since the 1960s and 70s, part of me cannot help but feel envious of these early years of your career. This was a golden age for the historical philosophy of science that saw spirited debates on the historical dynamics and direction of science as well as the factors underlying these. Alongside you, the most famous participants to these debates were the Austrian-born K. R. Popper and Paul Feyerabend and Hungarian-born Imre Lakatos, all of whom had migrated to the United Kingdom or the United States. As early as the 1930s, Popper had suggested in his book Logik der Forschung[vii] that falsification is the scientific method, which consists in demonstrating a theory as false or fallacious. If an observation contradicts predictions drawn from a certain theory, the theory must be discarded. But you clearly showed that this is impossible, as science is, in reality, full of anomalies and mutually contradictory findings. If Popper's view were correct, there would ultimately be no theories left! In order to advance, science requires of its practitioners a thick skin and a strong will. Science requires normal science.

In contrast to Popper’s assertions, you proposed that science should be regarded as puzzle-solving within the framework of a settled paradigm. The assumptions underlying the puzzle are not challenged, and the goal is instead to slowly complete it. Whole paradigms are only abandoned when prolonged scientific crises give rise to revolutions. During such watershed moments, anomalies, or contradictory observations and phenomena, play a crucial role as harbingers of new science.

It seems to me both daring and ingenious to use the analogy of a socio-political phenomenon such as a revolution to describe the nature of science, although, granted, this had already been done by your predecessors, including Alexandre Koyré[viii] and the English historian Herbert Butterfield.[ix] The original (and now secondary) meaning of the word “revolution” refers to an instance of something revolving around an axis in the context of e.g. celestial bodies in orbit. In light of its etymology, the term could thus be interpreted as cyclical change from normal science, dominated by a single paradigm, to a fundamental shift, which is again succeeded by a period of normality. But in the political sense a revolution is, of course, a forcible upending in which old laws and decrees are discarded and new ones enter into force. When monarchies are supplanted by democracies, the nobility are liable to lose their titles and former outlaws may assume the role of lawmakers. Perhaps, then, Einstein was the Lenin of physics and Darwin the Mandela of biology?

Scientific revolutions not only bring about a radical intellectual shift, but also reshape the standards by which intellectual activity is judged. This means that there is no single metric for comparing the relative merits of old and new theories. But to your critics, the concept of incommensurability contained the threat of irrationality. How can we evaluate theories of different paradigms against each other, and decide that one is superior? This would be akin to a comparison of, say, pears to bananas. And what does this imply for the idea of scientific progress? Is it not evident that, thanks to scientific inquiry, we now have a better understanding of the world than did our ancestors in the 19th century, for example? And does this not necessary imply that science has, in some sense, advanced?

To Lakatos, a Kuhnian theory shift resembles a sudden psychological, fundamentally mystical and extrarational change of perspective on the world and the phenomena and data it presents to us. Scientific revolutions would thus constitute a kind of gestaltist approach to changing perspectives on the same image, calling to mind the famous rabbit–duck illusion in which either a rabbit or a duck can be seen, but not both simultaneously. And as standards for evaluation also change as paradigms shift, the selection of new theories is based on their appeal, their “sexiness”, rather than rational grounds. Lakatos summed this idea up by stating that for Kuhn, explaining scientific change is an exercise in a kind of populist “mob psychology”. 

And there is no denying that you did, in fact, provide fodder for such discussions. Perhaps you were thinking of that unforgettable, hot (!) summer’s day in the 1940s, when you suddenly realized how past science should be read and examined. If we juxtapose Aristotle's scientific writings on the laws of motion, for instance, with the views of modern science, he quite simply appears silly. You confessed that you yourself had, on the basis of your earlier education, thought in this way, before it dawned on you how the scientists of the past should be understood. When we consider science in its proper historical context, we not only shed light on the thinking of its past practitioners, but may even come to see that thinking as sound given the assumptions from which they proceeded and the knowledge that was accessible to them at the time. Perhaps you sought to portray such changes of perspective as applicable to all scientific invention and rethinking?

Did you really mean to argue that science is not, in fact, a rational activity? The radical philosopher Feyerabend rejoiced at this conclusion drawn by many, and suggested that humanity start practising an epistemological anarchism that would allow all (ethically defensible) approaches and methods to be employed in the name of scientific progress. These could include, say, voodoo (although its ethical defensibility seems to me doubtful). These questions take us to the very core of scientific inquiry and the scientific community, as our culture strongly believes in science as a transgenerational, fundamentally rational activity.

I know that you did not mean to portray science as irrational, but merely sought to present evidence for the reasonable conclusion that (even) science cannot be considered an ideally rational pursuit; no programmable algorithm steers the practices and decisions of scientists. In your work, you pursued a kind of naturalization of rationality, which sees science as the best – albeit still imperfect – model for humanly rational activity. Your detractors are wide of the mark when they judge human-made science against a model of idealized rationality, which is perhaps only possible in certain closed mathematical systems.

You did not deny the existence of progress, but simply redefined it as an increase in our problem-solving capacity. In the course of history, science has continually gained in explanatory power and become an ever more effective tool for finding solutions to nature’s and humanity’s problems. Of course, it is an entirely separate discussion as to whether (even) science has the answers to the challenges of poverty and environmental crises, for example. Towards the end of your career, your discussions on the history of science as an evolutionary process took on an increasingly forceful tone. Perhaps we can all pin our hopes on science’s ability to diversify itself and develop new tools as new problems arise.

You recount an amusing experience at a meeting of student radicals in the 1960s or 70s in California. Along with many others, they had interpreted your writings on revolutions as a call to active rebellion against the standards and conventions of science, an exhortation to shatter the old and familiar. But in your mind the revolutionary idea was part of the natural dynamics of science, whose pressures sometimes force its practitioners to reorient themselves in radical ways, as patient, sustained effort proves old paradigms problematic.

This anecdote inspires me to reflect on how different today's world is, including from a social point of view. The 1960s and 70s saw efforts to dismantle structures and configurations of power that were perceived as repressive. And these efforts were relatively successful. Structures that constrain us and infringe on our human rights still exist, of course. They are now accompanied by a previously unseen phenomenon: fake news, wilful misdirection, and a new kind of doubt cast on scientific information. I wonder what reaction these would elicit from you. In this situation, would it not be prudent to defend rather than challenge (scientific) authority? It has been proposed that the historicization of science necessarily implies a relativization of truth and thus a weakening of the authority ascribed to scientific information, especially against the backdrop of the revolutionary shifts that science periodically undergoes. Could it be said that your work, by sowing such scepticism, helped pave the way for fake news and the doubters of science?

But any close reader of your writings will see that in spite of historical evolution, the same so-called epistemological values remain a constant feature of each successive paradigm and century: consistency, coherence, empirical accuracy, simplicity, and fertility. Towards the end of your career, you even described empirical

accuracy, scope, simplicity and so forth ... as necessarily enduring; because to abandon them would mean abandoning science and the knowledge it produces.[x]


Could it not be said that if doubt levelled at an old view or a proposition for a new one rests on these grounds, it is well-grounded, and thus rational? And without such grounds, is it nothing but frivolity or demagoguery? We can, and should, always endeavour to find new perspectives on science and knowledge, but we should always do it responsibly.

There is much work to be done in researching scientific activity and inquiry, i.e. the science of science, in both historical and modern perspective. This work, rewarding as it is not only to the academic community but to others as well, helps us all understand how and why knowledge is produced and revised. And, above all, it shines a spotlight on the rationality of science. In what sense is science rational? And in what sense is it not? Should we, as societies discussing science and knowledge, try to learn from the principles of scientific rationality? Could scientific debate, in turn, learn from the way social dialogue is conducted? There is no shortage of questions.

I only hope that many here in Oulu, in Finland, and beyond, choose to carry on your work!




[i] Kuhn, Thomas. 2000. The Road since the Structure. Chicago: Chicago University Press. Page 320.

[ii] The philosophy and history of science already existed as distinct disciplines. The 19th-century polymath and scientist William Whewell is considered the founder of the modern philosophy of science.

[iii] Kuhn, Thomas. 1994. Finnish translation: Tieteellisten vallankumousten rakenne. Helsinki. Art House. Originally published in English in 1962.

[iv] Kuhn 1962, 1.

[v] Hasok, Chang. 2004. Inventing Temperature: Measurement and Scientific Progress. Oxford: Oxford University Press; 2012. Is Water H2O?: Evidence, Realism and Pluralism (Boston Studies in the Philosophy and History of Science). Dordrecht: Springer.

[vi] See Chang, Is Water H2O?, chapter 1.2.4. “What Good is Phlogiston”.

[vii] Popper, Karl R. 1934. Logik der Forschung. Zur Erkenntnistheorie der modernen Naturwissenschaft. Mohr Siebeck. Published in English under the title The Logic of Scientific Discovery. Several editions.

[viii] Koyré, Alexandre. 1943. “Galileo and the Scientific Revolution of the Seventeenth Century.” The Philosophical Review 52, 333-348

[ix] See Butterfield, Herbert. 1951. The Origins of Modern Science 1300-1800. Simon and Schuster.

[x] Kuhn, Thomas. 2000. The Road since the Structure. Chicago: Chicago University Press. Page 252.


In Science Letters blog series, the researchers at the University of Oulu write letters to great scientists of the past or prominent figures of history. The letters commemorate the 60th anniversary of the University of Oulu and discuss important themes that are part of our world now and tomorrow.

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Last updated: 29.10.2019