The Inseparability of Scientific Fact and Theory in Kuhn’s Philosophy of Science

Every man takes the limits of his own field of vision for the limits of the world. – Arthur Schopenhauer

The Inseparability of Scientific Fact and Theory in Kuhn’s Philosophy of Science

Arif Afsar

Abstract: Scientists get the world through their conceptual frameworks. Unlike ordinary experience, scientific experience is not possible unless there is any prior theory or paradigm. Scientific facts, therefore, are different from facts in ordinary experience. A scientist’s experience is not ‘neutral’. Without any foregoing theory, what he receives would remain mere natural phenomena. These phenomena become scientific facts, only under some scientific theory or other. In the realm of science, fact and theory are entangled in such a manner that they are hardly separable. This article intends to concentrate on this ‘inseparability’ as a remarkable aspect of Thomas Kuhn’s philosophy of science.

The Structure of Scientific Revolutions itself brought about a ‘Copernican revolution’ in the history of the philosophy of science. It challenged many contemporary and previous views about science in several ways. One of the striking features of this encounter is the rejection of the concept of theory-independent fact. It is paradigms that define problems to be solved by the scientists. As scientists always receive the world through their paradigms there is no way to perceive any paradigm-independent fact whether in normal scientific practice or during revolutionary periods of paradigm shifts. Thomas Kuhn’s writing suggests that any scientific theory is a subset of a paradigm. It follows that anything that is not theory-independent cannot be paradigm-independent also.

Kuhn emphasized the way students of science are brought up to practice normal science as essentially a ‘puzzle-solving’ activity. They meet some exemplars from the beginning of their scientific education. An exemplar is a paradigm in the narrow sense. By ‘exemplars’ Kuhn means the concrete problem-solutions. He thinks that by doing exemplary problems a student of science absorbs ‘a time tested and group-licensed way of seeing’. Scientists design puzzles on former puzzle solutions. Kuhn is against the common-sense view that scientific theory and practice are different and independent things. The traditional view assumes that scientific knowledge is grounded on theories and rules, and problems are supplied to bring ease in their practice. But Kuhn’s ‘exemplars’ make scientific theory and practice indistinguishable. He tried to establish that no scientific practice is possible without any prior theory and simultaneously no theory is of importance in the absence of any exemplars. Puzzles in science are always paradigm-influenced. When we solve any puzzle we are guaranteed that it has a solution. This assurance comes from a paradigm that defines the puzzle. Although necessary, an assured solution is not enough for a puzzle. To be classified as a puzzle, a problem must be featured by other than an assured solution. There must be some rules that restrict adequate solutions and a series of steps by which these solutions are to be obtained.

…that enterprise seems an attempt to force nature into the preformed and relatively inflexible box that the paradigm supplies. No part of the aim of normal science is to call forth new sorts of phenomena: indeed those that will not fit the box are often not seen at all.1

Scientific revolution originates from a crisis when an existing paradigm starts to be more and more inefficient in solving compelling anomalies. But an anomaly, according to Kuhn, can be defined only against the background of a paradigm. Through a scientific revolution, the normal scientific tradition changes. The scientist, now, must re-culture his perception of his environment. He must learn to see a new gestalt in any familiar circumstance. The worlds in which the proponents of competing paradigms practice are different:

…the two groups of scientists see different things when they look from the same point in the same direction. Again, that is not to say that they can see anything they please. Both are looking at the world, and what they look at has not changed. But in some areas they see different things, and they see them in different relations one to the other…. Just because it is a transition between incommensurables, the transition between competing paradigms cannot be made a step at a time, forced by logic and neutral experience.2

Two loci of Kuhn’s view­ that there is no strict logical algorithm of a scientific revolution and that there can be no theory-independent scientific fact are marked now. We shall here stick to the second one:

Scientific fact and theory are not categorically separable, except perhaps within a single tradition of normal-scientific practice.3

When Kuhn says that facts are theory-laden, the word ‘fact’ actually refers to scientific facts. Objects or facts of natural or ‘neutral’ experience turn into scientific facts only when they are retrieved under this or that theory. Should we fail to realize this thing, we won’t be able to receive the Kuhnian message.

Let us consider three statements:

1. The sun rises in the east and sets in the west.

2. The sun moves around the earth.

3. The earth rotates on its axis.

Now, the second and the third are theory-laden, as far as we talk about theories in the realm of science. The second statement stands for the geocentric view and the third reveals an aspect of the heliocentric view. Unless we step into epistemological or phenomenological discourse the first statement can be regarded as representing our naive experience.

We shall look into another three statements for more clarity:

1. Milk is white.

2. Electrons bear a negative charge.

3. Mermaid is beautiful.

‘Milk’ has its referent in the spatio-temporal world, while on the contrary ‘mermaid’ does not. But the case of ‘electron’ and ‘charge’ is different. They refer to theoretical entities4 that we do not perceive but recognize as real for the sake of explaining some phenomena. So long the theories that proclaim electrons and charges as physical reality can deduce some consequences that can be experienced by our senses, the normal scientific practice is not to deny them.

We have no direct access to what it is we know, no rules or generalizations with which to express this knowledge. Rules which could supply that access would refer to stimuli not sensations, and stimuli we can know only through elaborate theory. In its absence, the knowledge embedded in the stimulus-to-sensation route remains tacit…. We do not see electrons, but rather their tracks or else bubbles of vapor in cloud chamber. We do not see electric currents at all, but rather the needle of an ammeter or galvanometer.5

The inseparability of theory and fact may be realized in various ways. Through a telescope, we can observe a ship approaching us although we may not see it yet with the naked eye. There is a difference between watching the moon through a telescope and seeing it without any telescope. If we accept the scientific explanation about the telescope and approve the scientific theories concerning refraction and reflection of light, only then can we say that the moon seen through the telescope is real because these theories are involved in constructing a telescope. Why should the presence of a distant star which cannot be observed without any telescope, be treated as a fact? It is possible only when we permit ‘theory-laden facts.’ Denying or disbelieving theories involved in making a telescope may tempt one to call it a “devil’s apparatus”. No doubt, refraction of light occurs when light passes through our eyes; and our eye is, with all its limitations, a sort of sophisticated apparatus. But eyes are simply natural and questions about our usual sense-experiences go back to somewhere else.

Kuhn never denied tangible facts and ordinary sense experience:

Observation and experience can and must drastically restrict the range of admissible scientific belief, else there would be no science.6

What Kuhn tries is to establish that mere sense experience and plain facts are not sufficient to give rise to a science. What else is still to be there? Kuhn answered it in many ways in The Structure of Scientific Revolutions. We shall now seek the answer somewhere else:

Both in life and in detective novels the crime is given. The detective must look for letters, fingerprints, bullets, guns, but at least he knows that a murder has been committed. This is not so for a scientist. It should not be difficult to imagine someone who knows absolutely nothing about electricity, since all the ancients lived happily enough without any knowledge of it. Let this man be given metal, gold foil, bottles, hard-rubber rod, flannel, in short, all the material required for performing our three experiments. He may be a very cultured person, but he will probably put wine into the bottles, use the flannel for cleaning, and never once entertain the idea of doing the things we have described. For the detective the crime is given, the problem formulated: who killed Cock Robin? The scientist must, at least in part, commit his own crime, as well as carry out the investigation.7

Whatever the ‘crime’ the scientist is supposed to commit, the consequence is the propagation of theoretical entities like electricity, charge, field etc. Even in the early years of the nineteenth century, there was nothing called ‘field’ in the domain of physics, but modern physics counts electromagnetic fields among real things:

The electromagnetic field is, for the modern physicist, as real as the chair on which he sits.8

It now seems fascinating to quote from Kuhn in this context:

Seeing water droplets or a needle against a numerical scale is a primitive perceptual experience for the man unacquainted with cloud chambers and ammeters. It thus requires contemplation, analysis, and interpretation (or else the intervention of external authority) before conclusions can be reached about electrons or currents. But the position of the man who has learned about these instruments and has much exemplary experience with them is very different, and there are corresponding differences in the way he processes the stimuli that reach him from them. Regarding the vapor in his breath on cold winter afternoon, his sensation may be same as that of a layman, but viewing a cloud chamber he sees (here literary) not droplets but the tracks of electrons, alpha particles, and so on. Those tracks are, if you will, criteria that he interprets as indices of the presence of the corresponding particles, but the route is both shorter and different from the one taken by the man who interprets droplets.9

It is now clear enough that scientific experience is different from our everyday experience. A scientist’s experience exceeds ‘neutral experience’. Without ‘a time tested and group-licensed way of seeing’ scientific perception is not possible. The same stimulus conveys different messages to a layman and a scientist. Without any prior theory, scientific perception is not possible at all. Again, the same stimulus may bear different meanings and become different facts to proponents of different theories.

Kuhn’s view is often compared to Kant’s theory of knowledge. There is indeed a resemblance between these two. According to Kant, the world of experience appears to us through the categories of our faculty of understanding. So, we are not able to perceive any category-independent fact or object. Now, if we replace ‘fact’ with ‘scientific fact’, and ‘faculty of understanding’ with ‘paradigm’, we get the similarity. But the difference is clear also. The faculty of understanding never changes. Space and time (as a priori forms of intuitions) and general categories like totality, reality, causality, possibility etc. always remain unchanged. On the contrary, a paradigm may triumph over another; and the history of science is a sequence of paradigms. The consequence of a paradigm shift brings new theories, rules, and canons of scientific practice. In addition, Kant’s endeavor is concerned with human knowledge, but Kuhn’s effort is to comprehend the nature of scientific practice.

Of course, more analogies can be drawn. Heisenberg’s uncertainty principle declares that we are not in a position to obtain an exact measurement of both the position and the velocity of an elementary particle; such measurement is impossible in principle. Elementary particles become affected by observation itself. According to Einstein’s special theory of relativity, an observer’s measurement of length, time and velocity depends on his frame of reference.

However, we are to grasp the difference again and should bear in mind that Kuhn’s concern is a ‘second-order criteriology’10. Heisenberg’s experimenter and Einstein’s observer are limited physically whereas Kuhn’s scientist is limited paradigmatically. In the special theory of relativity, the connection between coordinate systems is possible with the Lorentz transformation. In contrast, Kuhn denies the possibility of communication between paradigms, since they are incommensurable. The consequence of the incommensurability of paradigms is obvious; scientific facts are always theory-laden or paradigmatic.


1. Kuhn, Thomas S., The Structure of Scientific Revolutions, second edition, enlarged, Chicago: The University of Chicago Press, [1970], first published 1962, p.24.

2. Ibid., p.150.

3. Ibid., p.7.

4. “If we can observe something only through a telescope, we are still said to observe it. But if there are no conditions under which we can observe it, it is a theoretical entity; and when the theory-word is a part of a statement, that statement is said to be a theory.” – Hospers, John, An Introduction to Philosophical Analysis, Allied Publisher Private Ltd. seventh reprint 1988, p.236.

5. Kuhn, Thomas S., The Structure of Scientific Revolutions, second edition, enlarged, Chicago: The University of Chicago Press, [1970], first published 1962, p.24.

6. Ibid., p.4.

7. Einstein, Albert & Infeld, Leopold, The Evolution of Physics, Universal Book Stall, New Delhi, reprinted 1995, pp.75-76.

8. Ibid., p.151.

9. Kuhn, Thomas S., The Structure of Scientific Revolutions, second edition, enlarged, Chicago: The University of Chicago Press, [1970], first published 1962, p.197.

10. “A fourth view, which is the view adopted in this book, is that philosophy of science is a second-order criteriology. The philosopher of science seeks answers to such questions as:

“(1) What characteristics distinguish scientific inquiry from other types of investigation?

“(4) What is the cognitive status of scientific laws and principles?”

– Losee, John, A Historical Introduction to the Philosophy of Science, Oxford University Press, Second Edition, p.2.


Afsar, Arif:
A Study of The Nature of Scientific Progress in Kuhn’s Philosophy; submitted to the Department of Philosophy, Jahangirnagar University, in partial fulfillment of the requirements for the Master of Arts degree in Philosophy, September 1992.

Blackburn, Simon:
The Oxford Dictionary of Philosophy, Oxford University Press, [1996], first published 1994.

Einstein, Albert & Infeld, Leopold:
The Evolution of Physics, Universal Book Stall, New Delhi, reprinted 1995.

Gamow, George:
Biography of Physics, Hutchinson & Co. (Publishers) Ltd., London, first published 1962.

Hacking, Ian:
Introduction, Scientific Revolutions, edited by Ian Hacking; Oxford University Press, New York; [1981]

Hospers, John:
An Introduction to Philosophical Analysis, Allied Publisher Private Ltd. seventh reprint 1988.

Kant, Immanuel:
Critique of Pure Reason, edited by Vasilis Politis, Everyman, reprinted 1994.

Kuhn, Thomas S.:
The Structure of Scientific Revolutions, second edition, enlarged, Chicago: The University of Chicago Press, [1970], first published 1962.
– – –
‘Logic of Discovery or Psychology of Research?’ Criticism and The Growth of Knowledge, edited by Imre Lakatos & Alan Musgrave, Cambridge University Press, reprinted 1989, first published 1970.
– – –
‘Reflections on my Critics’, Criticism and The Growth of Knowledge, edited by Imre Lakatos & Alan Musgrave, Cambridge University Press, reprinted 1989, first published 1970.

Lipton, Peter:
‘Science, Philosophy of’, Microsoft Encarta Encyclopedia 2000.

Losee, John:
A Historical Introduction to the Philosophy of Science, Oxford University Press, Second Edition.

[Date of publication on the web: 30 November 2003]