Several generations of arts and humanities students have now encountered science solely through Kuhn's work, and it is the purpose of this essay to demonstrate that, brilliant as his thesis is, it is both flawed in its conception, and unfortunate in its consequences.

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Science can be seen as arrogant. To ‘arrogate’ is to take for oneself, and by implication it means to take something that one has no right to. The arrogance of science is seen by some as its claim to ‘truth’, claims that non-scientists are rarely in a position to verify. Hence a book on science, written by a scientist, and which suggests that science’s claim to ‘truth’ is unjustified, can be seductive. Such a book is Thomas Kuhn’s ‘The Structure of Scientific Revolutions’, first published in 1962, and now a classic of early post-modern writing. Several generations of arts and humanities students have now encountered science solely through Kuhn’s work, and it is the purpose of this essay to demonstrate that, brilliant as his thesis is, it is both flawed in its conception, and unfortunate in its consequences.

Before looking at Kuhn’s ideas let us take some examples from the history of science, presenting them in line with the conventional notion that science is a genuinely cumulative process of uncovering the nature of physical reality, the ‘prior given’ if you like of our shared universe. We will then see how Kuhn attempts to discredit this picture.

The Inverse-square law of Gravitation

We will start with the inverse-square law of gravitation, which marks the solution of a two-thousand-year old scientific problem. The historian Richard Tarnas in his book ‘The Passion of the Western Mind’ makes a brilliant presentation of what he calls ‘the problem of the planets’ as a central intellectual dilemma in the development of the Western mind. The word ‘planet’ comes from a Greek word meaning ‘to wander’, and was applied in ancient times to bright specks of light in the night sky that moved in irregular paths. The explanation of the planets’ movements occupied thinkers from Plato’s time to its eventual solution more than two thousand years later by Newton and his contemporaries. Saint Augustine for example tells us that the unsatisfactory answer to an astronomical question that he posed to a bishop of the Manichaean religion was one of the reasons that he abandoned it, eventually leading to his adopting the Christian faith. By Galileo’s time a complex theory of the heavenly bodies had evolved, called the Ptolemaic system, which involved concentric glassy spheres on which the planets and stars were placed, and whose motions were explained by rotations and epicycles. The system had become clumsy and could only adapt to new observations with difficulty. Its weakness was the firmly held belief that the Earth was at the centre of the Universe and that the sun and all other heavenly bodies rotated around it.

It was Copernicus who proposed the heliocentric theory, that the earth rotated round the sun. Galileo developed this further, and Kepler provided some of the mathematical basis for the theory. A group of scientists working with Newton pushed for the eventual scientific solution, the inverse square law of gravitation, which simply states that the force between two bodies is proportional to their masses and inversely proportional to their distance apart. By using this alongside Newton’s three laws of motion and making some other assumption such as that extended bodies like planets can be considered as point masses, all the known data on planetary movement could be accounted for. There was one exception however, the orbit of Mercury. The success of the new theory was due to its empirical base, that is the large number of observations made possible since the invention of the telescope. The anomalous orbit of Mercury demonstrates the pragmatic nature of science; if a theory accounts for 99.9% of the observations then that will do for now. Fig. 1 shows the Cavendish balance of 1798, which was used to verify the inverse square law under laboratory conditions.

(Caption) Fig. 1 The Cavendish balance. The success of celestial physics gave scientists the confidence to reproduce those conditions in the laboratory, a concept at the heart of the scientific method.

This account of the inverse-square law does no justice to the human and intellectual drama that went with it, or the sense of beauty that the intellect is pervaded with when confronted with the elegance and simplicity of this solution to a problem that had defeated the greatest minds of the West for over two millennia. The drama has many components of course, including the risks of religious persecution or contemporary ridicule, and the internecine struggles of the scientific community where co-operation between scientists was essential yet the rewards for claiming personal success were enormous.

At the heart of the intellectual drama is the nature of science as counter-intuitive. If we take science, contrary to Kuhn, as a gradual revelation of the deep structure of the objective world, then that structure reveals itself most unwillingly. Nature seems to present itself as a ‘whodunit’ with plenty of clues, but laid out in a contradictory fashion and in places where one least expects it. The inverse-square law solution to the problem of the planets involved the abandonment of a host of deeply ingrained ‘intuitions’. The first of these was the Earth as round, though even the Greeks had accepted this. The second was the Earth as moving around the sun, a concept that was profoundly challenging to our experience of the Earth as fixed and stable. The third was of orbits as elliptical instead of circular: this challenged the divine geometry of the ‘spheres’, which had been irrevocably fixed in the imagination of the medieval mind by Dante. The fourth was of the heavenly bodies as being impure, in particular the observation of sunspots. The fifth was the proposition that there were more than seven heavenly bodies. And so on. All these intuitions were deeply held and locked into a belief system that was later to unravel completely.

The Periodic Table of Elements

The discovery of the Periodic Table was an adventure with all the drama of the inverse-square law, and peopled by characters as turbulent and as brilliant as in any murder mystery. The great obstacle to its discovery was another deeply held intuition from the ancient world, that of the four elements, earth, air, fire and water. We find detailed accounts of the physical world in terms of these four elements in both ancient Greece and in other cultures such as Buddhist and Hindu. The central quest of chemistry was to explain natural phenomena, such as burning, plant growth, or geological formations in terms of these four elements, and it was with the greatest reluctance that new elements were introduced, and eventually the old scheme completely abandoned.

There are 105 known elements in the period table, so-called because elements with common properties group themselves periodically. The groups form rows which have respectively 2, 8, 8, and 18 elements in them, plus two longer series called the Lanthanides and Actinides with 32 elements. It later turned out that these seemingly arbitrary numbers are the solutions of a simple set of conditions within the atom, namely the Schroedinger equation. See fig. 2.

(Caption) Fig. 2 The Periodic Table. Although its structure emerged over a period of more than 200 years, the mathematical basis behind it was not established until the 1920s.

The periodic table provides a simple mathematical structure to underpin a huge range of phenomena, it orders the basis of chemistry, and its predictive power was demonstrated many times as the missing elements were found.

Invariance of the speed of light

Our third example, the invariance of the speed of light, is a single scientific ‘fact’ which, unlike the previous examples does not help us order an array of jumbled data or solve any previous problem. Instead it created such a serious new problem in science that a whole new range of theories developed out of it, namely Einstein’s relativity. The Michelson-Morley experiment of 1887 failed to detect the ‘ether’, the supposed carrier of light waves (see fig. 3).

(Caption) Fig. 3 The interferometer used by Michelson and Morley to investigate the existence of the ‘ether’. Their failure to detect it was the most significant and best-known null-result in science.

The invariance of the speed of light follows directly from absence of a carrier medium for light. Regardless of the speed of an observer towards or away from a light source in a vacuum, its measured velocity remains constant. The invariance of the speed of light and all its consequences are of course highly counter-intuitive. Unlike the idea that the earth is round and moving, or that there are more than seven heavenly bodies or four elements, it challenges our rational thinking at a deeper level. In fact we could say that not only is it an entirely unexpected discovery about our physical universe, it is almost an absurdity. Objects travelling close to the speed of light become smaller and heavier, and time dilates. One can accept the movement of the earth round the sun because we now have experience of riding on fast moving objects with little or no sensation of speed, such as in trains or planes. We have no difficulty abandoning seven heavenly bodies or four elements because we see those numbers as the product of archaic thinking. But the propositions of relativity are so outlandish that we rarely think about them. The system works however, predicting the exact outcome for the orbit of Mercury that the inverse square law failed to account for. Relativity fine-tunes Newtonian mechanics when dealing with very large scales or high speeds.

Khun’s Interpretation

Having looked now in some detail at three examples from science, we can explore Kuhn’s interpretation of the scientific process. Kuhn’s idea was that science does not progress by a cumulative process towards a better and better understanding of the natural world, but rather through scientific revolutions. Each revolution establishes a paradigm, that is a set of theories and methods the practice of which he calls ‘normal science’. When too many observations arise that do not fit the paradigm it is eventually overthrown, but not without a great deal of resistance, and often after a long period where the new data is either ignored or interpreted in such a way as to make no threat to the existing paradigm. The new paradigm is said to be incommensurable with the old. In our three examples, Newtonian mechanics became the revolutionary paradigm that overthrew Ptolemaic astronomy, the periodic table became the revolutionary paradigm that overthrew the chemistry of the ancients, and relativity the revolutionary paradigm that overthrew Newton. Kuhn argues this case well, and expands on the idea of ‘normal science’ as a process that inevitably supports the existing paradigm. We can see that once the old paradigm of the seven heavenly bodies was abandoned then scientists would seek more planets, thus supporting the new theory. In chemistry the establishment of the periodic table meant that the search was on for the missing elements, those that were needed to fill the rows but were as yet undiscovered. Relativity meant that the search was on to find the bending of light by massive bodies such as the sun, observations that were made in the eclipses of 1919 and 1922. Kuhn develops many examples to show that ‘normal science’ not only seeks to support the current paradigm, but actively avoids experiments that could undermine it. This goes on until the weight of counter-evidence is so strong that the next revolution is undertaken.

Kuhn pushes these ideas far beyond the argument as so far presented here however. Despite the thoughtful manner in which the arguments are presented that they are somewhat extreme, and taken as a whole give a perverse though seductive view of science. First let us look at the idea of the paradigm shift in reference to our three examples.

Quite naturally Kuhn cites Newtonian astronomy, represented here by the inverse-square law, as the paradigm that overthrew Ptolemaic astronomy. We have seen that it was a thorough revolution indeed, and the concept of incommensurability seems to apply well: nothing remained of the old system. Kuhn cites a number of other such revolutions, for example the phlogisten theory of combustion yielding to the oxygen theory. But both examples also provide us with the first doubts about Kuhn’s proposition. If we choose instead to think of the earlier paradigm as pre-scientific and the later one as science, then we are not so surprised to find that the transition was seen as a revolution, or that the old and new are incommensurable. The revolution is not a scientific one however. What about our periodic table? Did this not represent a paradigm shift and is the new science based on it not incommensurable with the old? Unfortunately the same objection could be made: the ancient chemistry based on the four elements was pre-scientific. This distinction is important: pre-scientific chemistry had no mathematical basis and no predictive power. Pre-scientific astronomy suffers from the same problem, but in contrast the inverse-square law not only had a mop-up rate for astronomical data previously unheard of, its mathematical basis had a much wider application, for example in optics and electromagnetism.

This leaves us with the example of relativistic mechanics as the revolution that overthrew Newtonian mechanics. Do we have a genuine example of a Kuhnian paradigm shift, one that marks a transition between two sciences?. Firstly, do we really have a case of incommensurability? Kuhn recognises that most scientists don’t see it that way, merely that Newton is the limiting case for low velocities, and hence Kuhn’s argument here is critical. He claims that because we see the universe in a different way than before, the terms referred to by Newton such as mass, length and time have a new meaning in in the physics of Einstein’s relativity, and hence there is no commonality between the two systems. In one sense this is true, that relativity is a radically different way of understanding mass, length and time. But does it overthrow the old? This question goes very deeply into Kuhn’s thesis, and in the long run its answer depends on who you are and how you think. It will be suggested here that for the philosophical mind the new paradigm in this case must overthrow the old (because the philosopher is constitutionally disinclined to be either empirical or pragmatic), while for the scientific mind they coexist. Scientists are not required to give meaning to what they discover, merely to test it against observation and to evaluate its use as a predictive method. Nowhere is this truer than in quantum theory where the interpretation or meaning has been hotly debated for over eighty years without resolution. Returning to Newtonian mechanics, we find that scientists use it on an everyday basis, and are probably more likely to retain even the concepts of mass, space and time that were implied by it than to use relativistic concepts. They rarely need to imagine for example that the mars-rocket they are building has to negotiate a curvature of space-time, rather than move in an appropriate path between two spheres in 3-dimensional space. When a relativistic correction is required it is the simplest piece of mathematics to apply it, even a bright school kid could do it.

If one removes all the examples of paradigm shifts that turn out to be from pre-science to science then a large part of Kuhn’s thesis is gone. What remains are transitions from one scientific paradigm to another, as in the relativity example. We have just seen that Kuhn’s insistence that Newtonian mechanics cannot be derived from relativistic mechanics is open to question. But Kuhn pushes his case far beyond this, using ideas from Gestalt psychology and other elements of the post-modernist viewpoint. By including pre-scientific paradigms in his discussion he makes it relatively easy to show that science can hold views that are thoroughly overturned in revolutions of thought, and hence that this is an ongoing process. If Newton overthrows Ptolemy and Einstein overthrows Newton, then it won’t be long before Einstein has had his day as well. Hence science’s claim to know the natural world is a false one. Kuhn reinforces this position, though it is not explicitly stated, by emphasising incommensurability, and the limited potential of normal science to find anything outside its paradigm. He also employs a measure of denigration, painting a portrait of the scientist as addicted to puzzle solving, and unwilling or unable to do anything useful like finding a cure for cancer or lasting world peace. He says for example ‘One of the reasons why normal science seems to progress so rapidly is that its practitioners concentrate on problems that only their own lack of ingenuity should keep them from solving’. It is true of course that much of science is humdrum, with only a small proportion of the scientific community participating in great discoveries and breakthroughs. But this is true of any field of human endeavour, and removes for us the pleasure and admiration for the great insights of science, and their pioneers. The reality of Kuhn’s book is that it takes every step possible to diminish the grandeur and beauty of science. He comes to bury it, not to praise it.

To sum up: Kuhn helps the lay person to disengage with science, and has found an audience eager to do so. The truth claims of science are challenging, but to disengage with science is paradoxically to maintain its hegemony. By denigrating science Kuhn fools the lay person into viewing it as a bumbling process of continual self-contradiction carried out by puzzle-solvers with addictive personalities and only rarely contributing to the needs of society. As a sociology or philosophy of science it may have merit, but it almost wilfully obliterates the subject of its attention. In contrast an effort to attract the non-scientist to science through an appreciation of its extraordinary power to reveal the deep structure of the manifold and manifest universe motivates a proper engagement, and this is what the great popular science writers of our time do so well. To love something for itself is to gain freedom from it, to falsely dismiss it is to remain its potential victim.