What Is This Thing Called Science Part 4

Advantages of falsificationism over inductivism.

With a summary of the basic features of falsificationism behind us, it is time to survey some of the advantages that this position can be said to have over the inductivist position according to which scientific knowledge is inductively derived-from given facts, which we discussed in earlier chapters.

We have seen that some facts, and especially experimental results, are in an important sense theory-dependent and fallible. This undermines those inductivists who require science to have an unproblematic and given factual foundation. The falsificationist recognises that facts as well as theories are fallible. Nevertheless, for the falsificationist there is an important set of facts that const.i.tute the testing ground for scientific theories. It consists of those factual claims that have survived severe tests. This does have the consequence that the factual basis for science is fallible, but this does not pose as big a problem for falsificationists as it does for inductivists, since the falsificationist seeks only constant improvement in science rather than demonstrations of truth or probable truth.

The inductivist had trouble specifying the criteria for a good inductive inference, and so had difficulty answering questions concerning the circ.u.mstances under which facts can be said to give significant support to theories. The falsificationist fares better in this respect. Facts give significant support to theories when they const.i.tute severe tests of that theory. The confirmations of novel predictions are important members of this category. This helps to explain why repet.i.tion of experiments does not result in a significant increase in the empirical support for a theory, a fact that the extreme inductivist has difficulty accommodating. The conduct of a particular experiment might well const.i.tute a severe test of a theory. However, if the experiment has been adequately performed and the theory has survived the test, then subsequent repet.i.tions of that same experiment will not be considered as severe a test of the theory, and so will become increasingly less able to offer significant support for it. Again, whereas the inductivist has problems explaining how knowledge of the un.o.bservable can ever be derived from observable facts, the falsificationist has no such problem. Claims about the un.o.bservable can be severely tested, and hence supported, by exploring their novel consequences.

We have seen that inductivists have trouble characterising and justifying the inductive inferences that are meant to show theories to be true or probably true. The falsificationist claims to bypa.s.s these problems by insisting that science does not involve induction. Deduction is used to reveal the consequences of theories so that they can be tested, and perhaps falsified. But no claims are made to the effect that the survival of tests shows a theory to be true or probably true. At best, the results of such tests show a theory to be an improvement on its predecessor. The falsificationist settles for progress rather than truth.

Further reading.

For Popper's mature reflections on his falsificationism see his 1983 text, Realism and the Aim of Science. Schilpp (1974), in the Library of Living Philosophers series, contains Popper's autobiography, a number of articles on his philosophy by critics, and Popper's reply to those critics, as well as a detailed bibliography of Popper's writings. Accessible overviews of Popper's views are Ackermann (1976) and O'He ar (1980). The modification of Popper's views involved in the section "Confirmation in the falsification account of science" is discussed in more detail in Chalmers (1973).

CHAPTER 7:.

The limitations of falsificationism.

Problems stemming from the logical situation.

The generalisations that const.i.tute scientific laws can never be logically deduced from a finite set of observable facts, whereas the falsity of a law can be logically deduced from a single observable fact with which it clashes. Establishing by observation that there is just one black swan falsifies "all swans are white". This is an unexceptional and undeniable point. However, using it as grounds to support a falsificationist philosophy of science is not as straightforward as it might seem. Problems emerge as soon as we progress beyond extremely simple examples, such as the one concerning the colour of swans, to more complicated cases that are closer to the kind of situation typically met with in science.

If the truth of some observation statement, 0, is given, then the falsity of a theory T which logically entails that 0 is not the case can be deduced. However, it is the falsificationists themselves who insist that the observation statements that const.i.tute the basis of science are theory-dependent and fallible. Consequently, a clash between T and 0 does not have the consequence that T is false. All that logically follows from the fact that T entails a prediction inconsistent with 0 is that either T or 0 is false, but logic alone cannot tell us which. When observation and experiment provide evidence that conflicts with the predictions of some law or theory, it may be the evidence which is at fault rather than the law or theory.

Nothing in the logic of the situation requires that it is always the law or theory that should be rejected on the occasion of a clash with observation or experiment. A fallible observation statement might be rejected and the fallible theory with which it clashes retained. This is precisely what was involved when Copernicus's theory was retained and the naked-eye observations of the sizes of Venus and Mars, which were logically inconsistent with that theory, discarded. It is also what is involved when modern specifications of the moon's trajectory are retained and estimates of its size based on unaided observation rejected. However securely based on observation or experiment a factual claim might be, the falsificationist's position makes it impossible to rule out the possibility that advances in scientific knowledge might reveal inadequacies in that claim. Consequently, straightforward, conclusive falsifications of theories by observation are not achievable.

The logical problems for falsification do not end here. "All swans are white" is certainly falsified if an instance of a non-white swan can be established. But simplified ill.u.s.trations of the logic of a falsification such as this disguise a serious difficulty for falsificationism that arises from the complexity of any realistic test situation. A realistic scientific theory will consist of a complex of universal statements rather than a single statement like "All swans are white". Further, if a theory is to be experimentally tested, then more will be involved than those statements that const.i.tute the theory under test. The theory will need to be augmented by auxiliary a.s.sumptions, such as laws and theories governing the use of any instruments used, for instance. In addition, in order to deduce some prediction the validity of which is to be experimentally tested, it will be necessary to add initial conditions such as a description of the experimental set-up. For instance, suppose an astronomical theory is to be tested by observing the position of some planet through a telescope. The theory must predict the orientation of the telescope necessary for a sighting of the planet at some specified time. The premises from which the prediction is derived will include the interconnected statements that const.i.tute the theory under test, initial conditions such as previous positions of the planet and sun, auxiliary a.s.sumptions such as those enabling corrections to be made for refraction of light from the planet in the earth's atmosphere, and so on. Now if the prediction that follows from this maze of premises turns out to be false (in our example, if the planet does not appear at the predicted location), then all that the logic of the situation permits us to conclude is that at least one of the premises must be false. It does not enable us to identify the faulty premise. It may be the theory under test that is at fault, but alternatively it may be an auxiliary a.s.sumption or some part of the description of the initial conditions that is responsible for the incorrect prediction. A theory cannot be conclusively falsified, because the possibility cannot be ruled out that some part of the complex test situation, other than the theory under test, is responsible for an erroneous prediction. This difficulty often goes under the name of the Duhern/Quine thesis, after Pierre Duhem (1962, pp. 183-8) who first raised it and William V.O. Quine (1961) who revived it.

Here are some examples from the history of astronomy that ill.u.s.trate the point.

In an example used previously, we discussed how Newton's theory was apparently refuted by the orbit of the planet Ura.n.u.s. In this case, it turned out not to be the theory that was at fault but the description of the initial conditions, which did not include a consideration of the yet-to-be-discovered planet Neptune. A second example involves an argument by means of which the Danish astronomer Tycho Brahe claimed to have refuted the Copernician theory a few decades after the first publication of that theory, If the earth orbits the sun, Brahe argued, then the direction in which a fixed star is observed from earth should vary during the course of the year as the earth moves from one side of the sun to the other. But when Brahe tried to detect t his predicted parallax with his instruments, which were the most accurate and sensitive ones in existence at the time, he failed. This led Brahe to conclude that the Copernican theory was false. With hindsight, it can be appreciated that it was not the Copernican theory that was responsible for the faulty prediction, but one of Brahe's auxiliary a.s.sumptions. Brahe's estimate of the distance of the fixed stars was many times too small. When his estimate is replaced by a more realistic one, the predicted parallax turns out to be too small to be detectable by Brahe's instruments.

A third example is a hypothetical one devised by Imre Lakatos (1970, pp. 100-401). It reads as follows: The story is about an imaginary case of planetary misbehaviour. A physicist of the pre Einsteinian era takes Newton's mechanics and his law of gravitation, N, the accepted initial conditions, I, and calculates, with their help, the path of a newly discovered small planet,p. But the planet deviates from the calculated path. Does our Newtonian physicist consider that the deviation was forbidden by Newton's theory and therefore that, once established, it refutes the theory N? No. He suggests that there must be a hitherto unknown planet p', which perturbs the path of p. He calculates the ma.s.s, orbit, etc. of this hypothetical planet and then asks an experimental astronomer to test his hypothesis. The planet p' is so small that even the biggest available telescopes cannot possibly observe it; the experimental astronomer applies for a research grant to build yet a bigger one. In three years time, the new telescope is ready. Were the unknown planet p' to be discovered, it would be hailed as a new victory of Newtonian science. But it is not. Does our scientist abandon Newton's theory and his idea of the perturbing planet? No. He suggests that a cloud of cosmic dust hides the planet from us. He calculates the location and properties of this cloud and asks for a research grant to send up a satellite to test his calculations. Were the satellite's instruments (possibly new ones, based on a little-tested theory) to record the existence of the conjectural cloud, the result would be hailed as an outstanding victory for Newtonian science. But the cloud is not found. Does our scientist abandon Newton's theory, together with the idea of the perturbing planet and the idea of the cloud which hides it? No. He suggests that there is some magnetic field in that region of the universe which disturbed the instruments of the satellite. A new satellite is sent up. Were the magnetic field to be found, Newtonians would celebrate a sensational victory. But it is not. Is this regarded as a refutation of Newtonian science? No. Either yet another ingenious auxiliary hypothesis is proposed or ... the whole story is buried in the dusty volumes of periodicals and the story never mentioned again.

If this story is regarded as a plausible one, it ill.u.s.trates how a theory can always be protected from falsification by deflecting the falsification to some other part of the compfek web of a.s.sumptions.

Falsificationism inadequate on historical grounds.

An embarra.s.sing historical fact for falsificationists is that if their methodology had been strictly adhered to by scientists then those theories generally regarded as being among the best examples of scientific theories would never have been developed because they would have been rejected in their infancy. Given any example of a cla.s.sic scientific theory whether at the time of its first proposal or at a later date, it is possible to find observational claims that were generally accepted at the time and were considered to be inconsistent with the theory. Nevertheless, those theories were not rejected, and it is fortunate for science that they were not. Some historical examples to support my claim follow.

In the early years of its life, Newton's gravitional theory was falsified by observations of the moon's...o...b..t. It took almost fifty years to deflect this falsification on to causes other than Newton's theory. Later in its life, the same theory was known to be inconsistent with the details of the orbit of the planet Mercury although scientists did not abandon the theory for that reason. It turned out that it was never possible to explain away this falsification in a way that protected Newton's theory.

A second example concerns Bohr's theory of the atom, and is due to Lakatos (1970, pp. 140-54). Early versions of the theory were inconsistent with the observation that some matter is stable for a time that exceeds about 10-8 seconds. According to the theory negatively charged electrons within atoms...o...b..t around positively charged nuclei. But according to the cla.s.sical electromagnetic theory presupposed by Bohr's theory orbiting electrons should radiate. The radiation would result in an orbiting electron losing energy and collapsing into the nucleus. The quant.i.tative details of cla.s.sical electromagnetism yield an estimated time of about 10-8 seconds for this collapse to occur. Fortunately, Bohr persevered with his theory, in spite of this falsification.

A third example concerns the kinetic theory and has the advantage that the falsification of that theory at birth was explicitly acknowledged by its originator. When Maxwell (1965, vol. 1, p. 409) published the first details of the kinetic theory of gases in 1859, in that very same paper he acknowledged the fact that the theory was falsified by measurements on the specific heats of gases. Eighteen years later, commenting on the consequences of the kinetic theory, Maxwell (1877) wrote: Some of these, no doubt, are very satisfactory to us in our present state of opinion about the const.i.tution of bodies, but there are others which are likely to startle us out of our complacency and perhaps ultimately to drive us out of all the hypotheses in which we have hitherto found refuge into that thoroughly conscious ignorance which is a prelude to every real advance in knowledge. All the important developments within the kinetic theory took place after this falsification. Once again, it is fortunate that the theory was not abandoned in the face of falsifications by measurements of the specific heats of gases, as the naive falsificationist would be forced to insist.

A fourth example, the Copernican Revolution, will be outlined in more detail in the following section. This example emphasises the difficulties that arise for the falsificationist when the complexities of major theory changes are taken into account. The example also sets the scene for a discussion of some more recent and more adequate attempts to characterise the essence of science and its methods.

The Copernican Revolution.

It was generally accepted in mediaeval Europe that the earth lies at the centre of a finite universe and that the sun, planets and stars...o...b..t around it. The physics and cosmology that provided the framework in which this astronomy was set was basically that developed by Aristotle in the fourth century BC. In the second century AD, Ptolemy devised a detailed astir nomical system that specified the orbits of the moon, the sun and all the planets. In the early decades of the sixteenth century, Copernicus devised a new astronomy, an astronomy involving a moving earth, which challenged the Aristotelian and Ptolemaic sys tem. According to the Copernican view, the earth is not stationary at the centre of the universe but orbits the sun along with the planets. By the time Copernicus's idea had been substantiated, the Aristotelian world view had been replaced by the Newtonian one. The details of the story of this major theory change, a change that took place over one and a half centuries, do not lend support to the methodologies advocated by the inductivists and falsificationists, and indicate a need for a different, perhaps more complexly structured, account of science and its growth.

When Copernicus first published the details of his new astronomy, in 1543, there were many arguments that could be, and were, levelled against it. Relative to the scientific knowledge of the time, these arguments were sound ones and Copernicus could not satisfactorily defend his theory against them. In order to appreciate this situation, it is necessary to be familiar with some aspects of the Aristotelian world view on which the arguments against Copernicus were based. A very brief sketch of some of the relevant points follows.

The Aristotelian universe was divided into two distinct regions. The sub-lunar region was the inner region, extending from the central earth to just inside the moon's...o...b..t. The super-lunar region was the remainder of the finite universe, extending from the moon's...o...b..t to the sphere of the stars, which marked the outer boundary of the universe. Nothing existed beyond the outer sphere, not even s.p.a.ce. Unfilled s.p.a.ce is an impossibility in the Aristotelian system. All celestial objects in the super-lunar region were made of an incorruptible element called Ether. Ether possessed a natural propensity to move around the centre of the universe in perfect circles. This basic idea became modified and extended in Ptolemy's astronomy. Since observations of planetary positions at various times could not be reconciled with circular, earth-centred orbits, Ptolemy introduced further circles, called epicycles, into the system. Planets moved in circles, or epicycles, the centres of which moved in circles around the earth. The orbits could be further refined by adding epicycles to epicycles etc. in such a way that the resulting system was compatible with observations of planetary positions and capable of predicting future planetary positions.

In contrast to the orderly, regular, incorruptible character of the super-lunar region, the sub-lunar region was marked by change, growth and decay, generation and corruption. All substances in the sub-lunar region were mixtures of four elements, air, earth, fire and water, and the relative proportions of elements in a mixture determined the properties of the substance so const.i.tuted. Each element had a natural place in the universe. The natural place for earth was at the centre of the universe; for water, on the surface of the earth; for air, in the region immediately above the surface of the earth; and for fire, at the top of the atmosphere, close to the moon's...o...b..t. Consequently, each earthly object would have a natural place in the sub-lunar region depending on the relative proportion of the four elements that it contained. Stones, being mostly earth, have a natural place near the centre of the earth, whereas flames, being mostly fire, have a natural place near to the moon's...o...b..t, and so on. All objects have a propensity to move in straight lines, upwards or downwards, towards their natural place. Thus stones have a natural motion straight downwards, towards the centre of the earth, and flames have a natural motion straight upwards, away from the centre of the earth. All motions other than natural motions require a cause. For instance, arrows need to be propelled by a bow and chariots need to be drawn by horses.

These, then, are the bare bones of the Aristotelian mechanics and cosmology that were presupposed by contemporaries of Copernicus, and which were utilised in arguments against a moving earth. Let us look at some of the forceful arguments against the Copernican system. Perhaps the argument that const.i.tuted the mdst serious threat to Copernicus was the so-called tower argument. It runs as follows. If the earth spins on its axis, as Copernicus had it, then any point on the earth's surface will move a considerable distance in a second. If a stone is dropped from the top of a tower erected on the moving earth, it will execute its natural motion and fall towards the centre of the earth. While it is doing so the tower will be sharing the motion of the earth, due to its spinning. Consequently, by the time the stone reaches the surface of the earth the tower will have moved around from the position it occupied at the beginning of the stone's downward journey. The stone should therefore strike the ground some distance from the foot of the tower. But this does not happen in practice. The stone strikes the ground at the base of the tower. It follows that the earth cannot be spinning and that Copernicus's theory is false.

Another mechanical argument against Copernicus concerns loose objects such as stones and philosophers resting on the surface of the earth. If the earth spins, why are such objects not flung from the earth's surface, as stones would be flung from the rim of a rotating wheel? And if the earth, as well as spinning, moves bodily around the sun, why doesn't it leave the moon behind?

Some arguments against Copernicus based on astronomical considerations have been mentioned earlier in this book. They involved the absence of parallax in the observed positions of the stars and the fact that Mars and Venus, as viewed by the naked eye, do not change size appreciably during the course of the year.

Because of the arguments I have mentioned, and others like them, the supporters of the Copernican theory were faced with serious difficulties. Copernicus himself was very much immersed in Aristotelian metaphysics and had no adequate response to them.

In view of the strength of the case against Copernicus, it might well be asked just what there was to be said in favour of the Copernican theory in 1543. The answer is, "not very much". The main attraction of the Copernican theory lay in the neat way it explained a number of features of planetary motion, which could be explained in the rival Ptolemaic theory only in an unattractive, artificial way. The features are the retrograde motion of the planets and the fact that, unlike the other planets, Mercury and Venus always remain in the proximity of the sun. A planet at regular intervals regresses, that is, stops its westward motion among the stars (as viewed from earth) and for a short time retraces its path eastward before continuing its journey westward once again. In the Ptolemaic system, retrograde motion was explained by the somewhat ad hoc manoeuvre of adding epicycles especially designed for the purpose. In the Copernican system, no such artificial move is necessary. Retrograde motion is a natural consequence of the fact that the earth and the planets together orbit the sun against the background of the fixed stars. Similar remarks apply to the problem of the constant proximity of the sun, Mercury and Venus. This is a natural consequence of the Copernican system once it is established that the orbits of Mercury and Venus are inside that of the earth. In the Ptolemaic system, the orbits of the sun, Mercury and Venus have to be artificially linked together to achieve the required result.

Thus there were some mathematical features of the Copernican theory that were in its favour. Apart from these, the two rival systems were more or less on a par as far as simplicity and accord with observations of planetary positions are concerned. Circular sun-centred orbits cannot be reconciled with observation, so that Copernicus, like Ptolemy, needed to add epicycles, and the total number of epicycles needed to produce orbits in accord with known observations was about the same for the two systems. In 1543 the arguments from mathematical simplicity that worked in favour of Copernicus could not be regarded as an adequate counter to the mechanical and astronomical arguments that worked against him. Nevertheless, a number of mathematically capable natural philosophers were to be attracted to the Copernican system, and their efforts to defend it became increasingly successful over the next hundred years or so.

The person who contributed most significantly to the defence of the Copernican system was Galileo. He did so in two ways. First, he used a telescope to observe the heavens, and in so doing he transformed the observational data that the Copernican theory was required to explain. Second, he devised the beginnings of a new mechanics that was to replace Aristotelian mechanics and with reference to which the mechanical arguments against Copernicus were defused.

When, in 1609, Galileo constructed his first telescopes and trained them on the heavens, he made dramatic discoveries. He saw that there were many stars invisible to the naked eye. He saw that Jupiter has moons and he saw that the surface of the earth's moon is covered with mountains and craters. He also observed that the apparent size of Mars and Venus, as viewed through the telescope, changed in the way predicted by the Copernican system. Later, Galileo was to confirm that Venus has phases like the moon, a fact that could be straightforwardly accommodated into the Copernican, but not the Ptolemaic, system. The moons of Jupiter defused the Aristotelian argument against Copernicus based on the fact that the moon stays with an allegedly moving earth. For now Aristotelians were faced with the same problem with respect to Jupiter and its moons. The earthlike surface of the moon undermined the Aristotelian distinction between the perfect, incorruptible heavens and the changing, corruptible earth. The discovery of the phases of Venus marked a success for the Copernicans and a new problem for the Ptolemaics. It is undeniable that once the observations made by Galileo through his telescope are accepted, the difficulties facing the Copernican theory are diminished.

The foregoing remarks on Galileo and the telescope raise a serious epistemological problem. Why should observations through a telescope be preferred to naked-eye observations? One answer to this question might utilise an optical theory of the telescope that explains its magnifying properties and that also gives an account of the various aberrations to which we can expect telescopic images to be subject. But Galileo himself did not utilise an optical theory for that purpose. The first optical theory capable of giving support in this direction was devised by Galileo's contemporary, Kepler, early in the sixteenth century, and this theory was improved and augmented in later decades. A second way of facing our question concerning the superiority of telescopic to naked-eye observations is to demonstrate the effectiveness of the telescope in a practical way, by focusing it on distant towers, ships, etc. and demonstrating how the instrument magnifies and renders objects more distinctly visible. However, there is a difficulty with this kind of justification of the use of the telescope in astronomy. When terrestrial objects are viewed through a telescope, it is possible to separate the viewed object from aberrations contributed by the telescope because of the observer's familiarity with what a tower, a ship, etc. look like. This does not apply when an observer searches the heavens for he knows not what. It is significant in this respect that Galileo's drawing of the moon's surface as he saw it through a telescope contains some craters that do not in fact exist there. Presumably those "craters" were aberrations arising from the functioning of Galileo's far-from-perfect telescopes. Enough has been said in this paragraph to indicate that the justification of telescopic observations was no simple, straightforward matter. Those adversaries of Galileo who queried his findings were not all stupid, stubborn reactionaries. Justifications were forthcoming, and became more and more adequate as better and better telescopes were constructed and as optical theories of their functioning were developed. But all this took time.

Galileo's greatest contribution to science was his work in mechanics. He laid some of the foundations of the Newtonian mechanics that was to replace Aristotle's. He distinguished clearly between velocity and acceleration and a.s.serted that freely falling objects move with a constant acceleration that is independent of their weight, dropping a distance proportional to the square of the time of fall. He denied the Aristotelian claim that all motion requires a cause. He argued that the velocity of an object moving horizontally, along a line concentric with the earth, should neither increase nor decrease since it is neither rising nor falling. He a.n.a.lysed projectile motion by resolving the motion of a projectile into a horizontal component moving with a constant velocity and a vertical component subject to a constant acceleration downwards. He showed that the resulting path of a projectile was a parabola. He developed the concept of relative motion and argued that the uniform motion of a system could not be detected by mechanical means without access to some reference point outside of the system.

These major developments were not achieved instantaneously by Galileo. They emerged gradually over a period of half a century, culminating in his book Two New Sciences (1974), which was first published in 1638, almost a century after the publication of Copernicus's major work. Galileo rendered his new conceptions meaningful and increasingly more precise by means of ill.u.s.trations and thought experiments. Occasionally, Galileo described actual experiments, for instance experiments involving the rolling of spheres down inclined planes, although just how many of these Galileo actually performed is a matter of some dispute.

Galileo's new mechanics enabled the Copernican system to be defended against some of the objections to it mentioned above. An object held at the top of a tower and sharing with the tower a circular motion around the earth's centre will continue in that motion, along with the tower, after it is dropped and will consequently strike the ground at the foot of the tower, consistent with experience. Galileo took the argument further and claimed that the correctness of his views on horizontal motion could be demonstrated by dropping a stone from the top of the mast of a uniformly moving ship and noting that it strikes the deck at the foot of the mast, although Galileo did not claim to have performed the experiment. Galileo was less successful in explaining why loose objects are not flung from the surface of a spinning earth.

Although the bulk of Galileo's scientific work was designed to strengthen the Copernican theory, Galileo did not himself devise a detailed astronomy, and seemed to follow the Aristotelians in their preference for circular orbits. It was Galileo's contemporary Kepler, who contributed a major breakthrough in that direction when he discovered that each planetary orbit could be represented by a single ellipse, with the sun at one focus. This eliminated the complex system of epicycles that both Copernicus and Ptolemy had found necessary. No similar simplification is possible in the Ptolemaic, earth-centred system. Kepler had at his disposal Tycho Brahe's recordings of planetary positions, which were more accurate than those available to Copernicus. After a painstaking a.n.a.lysis of the data, Kepler arrived at his three laws of planetary motion, that planets move in elliptical orbits around the sun, that a line joining a planet to the sun covers equal areas in equal times, and that the square of the period of a planet is proportional to the cube of its mean distance from the sun.

Galileo and Kepler certainly strengthened the case in favour of the Copernican theory. However, more developments were necessary before that theory was securely based on a comprehensive physics. Newton was able to take advantage of the work of Galileo, Kepler and others to construct that comprehensive physics that he published in his Principia in 1687. He spelt out a clear conception of force as the cause of acceleration rather than motion, a conception that had been present in a somewhat confused way in the writings of Galileo and Kepler. Newton replaced Galileo's views on inertia with his law of linear inertia, according to which bodies continue to move in straight lines at uniform speed unless acted on by a force. Another major contribution by Newton was of course his law of gravitation. This enabled Newton to explain the approximate correctness of Kepler's laws of planetary motion and Galileo's law of free fall. In the Newtonian system, the realms of the celestial bodies and of earthly bodies were unified, each set of bodies moving under the influence of forces according to Newton's laws of motion. Once Newton's physics had been const.i.tuted, it was possible to apply it in detail to astronomy. It was possible, for instance, to investigate the details of the moon's...o...b..t, taking into account its finite size, the spin of the earth, the wobble of the earth upon its axis, and so on. It was also possible to investigate the departure of the planets from Kepler's laws due to the finite ma.s.s of the sun, interplanetary forces, etc. Developments such as these were to occupy some of Newton's successors for the next couple of centuries.

The story I have sketched here should be sufficient to indicate that the Copernican Revolution did not take place at the drop of a hat or two from the Leaning Tower of Pisa. It is also clear that neither the inductivists nor the falsificationists give an account of science that is compatible with it. New concepts of force and inertia did not come about as a result of careful observation and experiment. Nor did they come about through the falsification of bold conjectures and the continual replacement of one bold conjecture by another. Early formulations of the new theory involving imperfectly formulated novel conceptions, were persevered with and developed in spite of apparent falsifications. It was only after a new system of physics had been devised, a process that involved the intellectual and practical labour of many scientists over several centuries, that the new theory could be successfully matched with the results of observation and experiment in a detailed way. No account of science can be regarded as anywhere near adequate unless it can accommodate such factors.

Inadequacies of the falsificationist demarcation criterion and Popper's response.

Popper made a seductive case for his criterion of demarcation between science and non- or pseudo-science. Scientific theories should be falsifiable, that is, they should have consequences that can be tested by observation or experiment. One weakness of this criterion, if unqualified, is that it is too easily satisfied and, in particular, satisfied by many knowledge claims that Popper, for one, would wish to cla.s.sify as non-science. Astrologists do make claims that are falsifiable (and frequently falsified), while the horoscopes published in newspapers and journals do make falsifiable (as well as unfalsifiable) claims. The same "Your Stars" newspaper column that yielded the (unfalsifiable) prediction that "luck is possible in sporting speculation" quoted in chapter 5 also promised those whose birthday is on March 28 that "a new lover will put a sparkle in your eye and improve social activities", a promise that is certainly falsifiable. Any fundamentalist brand of Christianity that insists that the Bible be taken literally is falsifiable. The claim in Genesis that G.o.d created the seas and populated them with fish would be falsified if there were no sea and/or no fish. Popper himself notes that Freudian theory, to the extent that it construes dreams as wish fulfillments, faces the threat of falsification by nightmares.

One response that the falsificationist can give to this observation is to note that theories must not only be falsifiable, but must also be not falsified. This might eliminate the claims of horoscopes to be scientific, and Popper argues that it eliminates Freudian theory. But this solution cannot be adopted too readily lest it eliminate everything that the falsificationists wish to retain as scientific, for we have seen that most scientific theories have their problems and clash with some accepted observation or other. So it becomes allowable, according to the sophisticated falsificationist, to modify theories in the face of apparent falsifications, and even to hang on to theories in spite of falsifications in the hope that the problem can be solved in the future. This kind of response is captured in the following pa.s.sage from Popper (1974, p. 55) which is an attempt by him to confront difficulties of the kind I am raising here.

I have always stressed the need for some dogmatism: the dogmatic scientist has an important role to play. If we give into criticism too easily, we shall never find out where the real power of our theories lies.

It is my view that this pa.s.sage is ill.u.s.trative of the extent to which falsificationism faces severe difficulties in the light of the kinds of criticism raised in this chapter. The thrust of falsificationism is to emphasise the critical component of science. Our theories are to be subject to ruthless criticism so that the inadequate ones can be weeded out and replaced by more adequate ones. Faced with the problems surrounding the degree of definiteness with which theories can be falsified, Popper admits that it is often necessary to retain theories in spite of apparent falsifications. So although ruthless criticism is recommended, what would appear to be its opposite, dogmatism, has a positive role to play too. One might well wonder what is left of falsificationism once dogmatism is allowed a key role. Further, if both a critical and a dogmatic att.i.tude can be condoned, then it is difficult to see what att.i.tudes are ruled out. (It would be ironic if the highly qualified version of falsificationism became so weak as to rule out nothing, thereby clashing with the main intuition that led Popper to formulate it!)

Further reading.

A range of criticisms of Popper's falsificationism are contained in Schilpp (1974). Criticism of all but the most sophisticated brand of falsificationism is marshalled in Lakatos (1970). Many of the points made in this chapter concerning the incompatibility of falsificationism with the Copernican revolution were taken from Feyerabend (1975).

Lakatos and Musgrave (1970) contains articles that critically compare Popper's position with those of Thomas Kuhn, whose views are discussed in the next chapter. There are some finely tuned criticisms of Popper's position in Mayo (1996).

CHAPTER 8:.

Theories as structures I: Kuhn's paradigms.

Theories as structures.

The sketch of the Copernican Revolution outlined in the previous chapter suggests that the inductivist and falsificationist accounts of science are too piecemeal. Concentrating on the relationship between theories and individual observation statements or sets of them, they seem to fail to grasp the complexity of the mode of development of major theories. Since the 1960s it has become common to conclude from this that a more adequate account of science must proceed from an understanding of the theoretical franl ieworks in which scientific activity takes place. The next three chapters are concerned with three influential accounts of science that have resulted from an adoption of this approach. In chapter 13 we will have reason to question whether the "theory-dominated" view of science has gone too far.) One reason why there is seen to be a need to view theories as structures stems from the history of science. Historical study reveals that the evolution and progress of major sciences exhibit a structure that is not captured by the inductivist and falsificationist accounts. The Copernican Revolution has already supplied us with an example. The notion can be further enhanced by reflecting on the fact that for a couple of centuries after Newton, physics was carried out in the Newtonian framework, until that framework was challenged by relativity and quantum theory at the beginning of the century. However, the historical argument is not the only reason why some have seen the need to concentrate on theoretical frameworks. A more general, philosophical argument is closely linked with the ways in which observation can be said to be theory-dependent. In chapter 1 it was stressed that observation statements must be expressed in the language of some theory Consequently, it is argued, the statements, and the concepts figuring in them, will be as precise and informative as the theory in whose language they are formed is precise and informative. For instance, I think it will be agreed that the Newtonian concept of ma.s.s has a more precise meaning than the concept of democracy, say. It is plausible to suggest that the reason for the relatively precise meaning of the former stems from the fact that the concept plays a specific, well-defined role in a precise, closely knit theory, Newtonian mechanics. By contrast, the social theories in which the concept "democracy" occurs are vague and multifarious. If this suggested close connection between precision of meaning of a term or statement and the role played by that term or statement in a theory is valid, then the need for coherently structured theories would seem to follow directly from it.

The dependence of the meaning of concepts on the structure of the theory in which they occur, and the dependence of the precision of the former on the precision and degree of coherence of the latter, can be made plausible by noting the limitations of some of the alternative ways in which a concept might be thought to acquire meaning. One such alternative is the view that concepts acquire their meaning by way of a definition. Definitions must be rejected as a fundamental way of establishing meanings because concepts can only be defined in terms of other concepts, the meanings of which are given. If the meanings of these latter concepts are themselves established by definition, it is clear that an infinite regress will result unless the meanings of some concepts are known by other means. A dictionary is useless unless we already know the meanings of many words. Newton could not define ma.s.s or force in terms of previously available concepts. It was necessary for him to transcend the limits of the old conceptual framework by developing a new one. A second alternative is the suggestion that concepts acquire their meaning by way of ostensive definition. We saw, in our discussion of a child learning the meaning of "apple" in chapter 1, that this is difficult to sustain even in the case of an elementary notion like "apple". It is even more implausible when it comes to the definition of something like "ma.s.s" in mechanics or "electric field" in electromagnetism.

The claim that concepts derive their meaning at least in part from the role they play in a theory can be given support by the following historical reflections. Contrary to popular myth, experiment was by no means the key to Galileo's innovations in mechanics. Many of the "experiments".....he refers to in articulating his theory are thought experiments.. This can appear paradoxical for those who see novel theories arising as a result of experiment, but it is quite comprehensible if it is accepted that precise experimentation can only yielding predictions in the form of precise observation statements. Galileo, it might be argued, was in the process of making a major contribution to the building of a new mechanics that was to prove capable of supporting detailed experimentation at a later stage. It need not be surprising that his efforts involved thought experiments, a.n.a.logies and ill.u.s.trative metaphors rather than detailed experimentation. A case could be made to the effect that the typical history of a concept, whether it be "chemical element", "atom", "the unconscious" or whatever, involves the initial emergence of the concept as a vague idea, followed by its gradual clarification as the theory in which it plays a part takes a more precise and coherent form. The emergence of the concept of an electric field can be construed in a way that supports such a view. When the concept was first introduced by Faraday in the first half of the nineteenth century it was very vague, and was articulated with the aid of mechanical a.n.a.logies involving such things as stretched strings and metaphorical uses of such terms as "tension", "power" and "force". The field concept became increasingly better defined as the relationship between the electric field and other electromagnetic quant.i.ties became more clearly specified. Once Maxwell had introduced his displacement current, again with the aid of mechanical a.n.a.logies, it was possible to bring great coherence to the theory in the form of Maxwell's equations, which clearly specified the interrelationship between all the electromagnetic quant.i.ties. It was not long before the ether, which had been considered to be the mechanical seat of the fields, could be dispensed with, leaving the fields as clearly defined concepts in their own right.

In this section I have attempted to construct a rationale for approaching science by way of the theoretical frameworks within which scientific work and argumentation take place. In this and the following two chapters we look at the work of three important philosophers of science who have pursued this idea.

Introducing Thomas Kuhn.

Inductivist and falsificationist accounts of science were challenged in a major way by Thomas Kuhn (1970a) in his book The Structure of Scientific Revolutions, first published in 1962, and then republished with a clarificatory PostScript eight years later. His views have reverberated in the philosophy of science ever since. Kuhn started his academic career as a physicist and then turned his attention to the history of science. On doing so, he found that his preconceptions about .the nature of science were shattered He came to believe that traditional accounts of science, whether inductivist or falsifi-. cationist, do not bear comparison with historical evidence. Kuhn's account of science was subsequently developed as an attempt to give a theory more in keeping with the historical situation as he saw it. A key feature of his theory is the emphasis placed on the revolutionary character of scientific progress, where a revolution involves the abandonment of one theoretical structure and its replacement by another, incompatible one. Another important feature is the important role played by the sociological characteristics of scientific communities.

Kuhn's picture of the way a science progresses can be summarised by the following open-ended scheme: pre-science - normal science - crisis - revolution - new normal science - new crisis The disorganised and diverse activity that precedes the formation of a science eventually becomes structured and directed when a single paradigm becomes adhered to by a scientific community. A paradigm is made up of the general theoretical a.s.sumptions and laws and the techniques for their application that the members of a particular scientific community adopt. Workers within a paradigm, whether it be Newtonian mechanics, wave optics, a.n.a.lytical chemistry or whatever, practise what Kuhn calls normal science. Normal scientists will articulate and develop the paradigm in their attempt to account for and accommodate the behaviour of some relevant aspects of the real world as revealed through the results of experimentation. In doing so, they will inevitably experience difficulties and encounter apparent falsifications. If difficulties of that kind get out of hand, a crisis state develops. A crisis is resolved when an entirely new paradigm emerges and attracts the allegiance of more and more scientists until eventually the original, problem-ridden paradigm is abandoned. The discontinuous change const.i.tutes a scien tific revolution. The new paradigm, full of promise and not beset by apparently insuperable difficulties, now guides new normal scientific activity until it too runs into serious trouble and a new crisis followed by a new revolution results.

With this resume as a foretaste, let us look at the various components of Kuhn's scheme in more detail.

Paradigms and normal science.

A mature science is governed by a single paradigm.1 The paradigm sets the standards for legitimate work within the science it governs. It coordinates and directs the "puzzle-solving" activity of the groups of normal scientists who work within it. The existence of a paradigm capable of supporting a normal science tradition is the characteristic that distinguishes science from non-science, according to Kuhn. Newtonian mechanics, wave optics and cla.s.sical electromagnetism all const.i.tuted and perhaps const.i.tute paradigms and qualify as sciences. Much of modern sociology lacks a paradigm and consequently fails to qualify as science.

As will be explained below, it is of the nature of a paradigm to belie precise definition. Nevertheless, it is possible to describe some of the typical components that go to make up a paradigm. Among the components will be explicitly stated fundamental laws and theoretical a.s.sumptions. Thus Newton's laws of motion form part of the Newtonian paradigm and Maxwell's equations form part of the paradigm that const.i.tutes cla.s.sical electromagnetic theory. Paradigms will also include standard ways of applying the fundamental laws to a variety of types of situation. For instance, the Newtonian paradigm will include methods of applying Newton's laws to planetary motion, pendulums, billiard-ball collisions, and so on. Instrumentation and instrumental techniques necessary for bringing the laws of the paradigm to bear on the real world will also be included in the paradigm. The application of the Newtonian paradigm in astronomy involves the use of a variety of approved kinds of telescope, together with techniques for their use and a variety of techniques for the correction of the data collected with their aid. A further component of paradigms consists of some very general, metaphysical principles that guide work within a paradigm. Throughout the nineteenth century the Newtonian paradigm was governed by an a.s.sumption something like, "The whole of the physical world is to be explained as a mechanical system operating under the influence of various forces according to the dictates of Newton's laws of motion", and the Cartesian program in the seventeenth century involved the principle, "There is no void and the physical universe is a big clockwork in which all forces take the form of a push". Finally, all paradigms will contain some very general methodological prescriptions such as, "Make serious attempts to match your paradigm with nature", or "Treat failures in attempts to match a paradigm with nature as serious problems".

Normal science involves detailed attempts to articulate a paradigm with the aim of improving the match between it and nature. A paradigm will always be sufficiently imprecise and open-ended to leave plenty of that kind of work to be done.

Kuhn portrays not alai science as a puzzle-solving activity governed by the rules of a paradigm. The puzzles will be of both a theoretical and an experimental nature. Within the Newtonian paradigm, for instance, typical theoretical puzzles involve devising mathematical techniques for dealing with the motion of a planet subject to more than one attractive force, and developing a.s.sumptions suitable for applying Newton's laws to the motion of fluids. Experimental puzzles included the improvement of the accuracy of telescopic observations and the development of experimental techniques capable of yielding reliable measurements of the gravitational constant. Normal scientists must presuppose that a paradigm provides the means for the solution of the puzzles posed within it. A failure to solve a puzzle is seen as a failure of the scientist rather than as an inadequacy of the paradigm. Puzzles that resist solution are seen as anomalies rather than as falsifications of a paradigm. Kuhn recognises that all paradigms will contain some anomalies (for example the Copernican theory and the apparent size of Venus or the Newtonian paradigm and the orbit of Mercury) and rejects all brands of falsificationism.

Normal scientists must be uncritical of the paradigm in which they work. It is only by being so that they are able to concentrate their efforts on the detailed articulation of the paradigm and to perform the esoteric work necessary to probe nature in depth. It is the lack of disagreement over fundamentals that distinguishes mature, normal science from the relatively disorganised activity of immature pre science. According to Kuhn, the latter is characterised by total disagreement and constant debate over fundamentals, so much so that it is impossible to get down to detailed, esoteric work. There will be almost as many theories as there are workers in the field and each theoretician will be obliged to start afresh and justify his or her own particular approach. Kuhn offers optics before Newton as an example. There was a wide diversity of theories about the nature of light from the time of the ancients up to Newton. No general agreement was reached and no detailed, generally accepted theory emerged before Newton proposed and defended his particle theory The rival theorists of the pre-science period disagreed not only over fundamental theoretical a.s.sumptions but also over the kinds of observational phenomena that were relevant to their theories. Insofar as Kuhn recognises the role played by a paradigm in guiding the search for and interpretation of observable phenomena, he accommodates the sense in which observation and experiment can be said to be theory-dependent.

Kuhn insists that there is more to a paradigm than what can be explicitly laid down in the form of explicit rules and directions. He invokes Wittgenstein's discussion of the notion of "game" to ill.u.s.trate some of what he means. Wittgenstein argued that it is not possible to spell out necessary and sufficient conditions for an activity to be a game. When one tries, one invariably finds an activity that one's definition includes but that one would not want to count as a game, or an activity that the definition excludes but that one would want to count as a game. Kuhn claims that the same situation exists with respect to paradigms. If one tries to give a precise and explicit characterisation of some paradigm in the history of science or in present-day science, it always turns out that some work within the paradigm violates the characterisation. However, Kuhn insists that this state of affairs does not render the concept of paradigm untenable any more than the similar situation with respect to "game" rules out legitimate use of that concept. Even though there is no complete, explicit characterisation, individual scientists acquire knowledge of a paradigm through their scientific education. By solving standard problems, performing standard experiments and eventually by doing a piece of research under a supervisor who is already a skilled pract.i.tioner within the paradigm, an aspiring scientist becomes acquainted with the methods, the techniques and the standards of that paradigm. The aspiring scientist will be no more able to give an explicit account of the methods and skills he or she has acquired than a master-carpenter will be able to fully describe what lies behind his or her skills. Much of the normal scientist's knowledge will be tacit, in the sense developed by Michael Polanyi (1973).

Because of the way they are trained, and need to be trained if they are to work efficiently, typical normal scientists will be unaware of and unable to articulate the precise nature of the paradigm in which they work. However, it does not follow from this that a scientist will not be able to articulate the presuppositions involved in the paradigm should the need arise. Such a need will arise when a paradigm is threatened by a rival. In those circ.u.mstances, it will be necessary to attempt to spell out the general laws and metaphysical and methodological principles involved in a paradigm in order to defend them against the alternatives involved in the threatening new paradigm. The next section summarises Kuhn's account of how a paradigm can run into trouble and be replaced by a rival.

Crisis and revolution.

Normal scientists work confidently within a well-defined area dictated by a paradigm. The paradigm presents them with a set of definite problems together with methods that they are confident will be adequate for the solution of the problems. If they blame the paradigm for any failure to solve a problem, they will be open to the same charges as the carpenter who blames his tools. Nevertheless, failures will be encountered and such failures can eventually attain a degree of seriousness that const.i.tutes a serious crisis for the paradigm and may lead to the rejection of a paradigm and its replacement by an incompatible alternative.

The mere existence of unsolved puzzles within a paradigm does not const.i.tute a crisis. Kuhn recognises that paradigms will always encounter difficulties. There will always be >anomalies. It is only under special sets of conditions that the anomalies can develop in such a way as to undermine confidence in the paradigm. An anomaly will be regarded as particularly serious if it is seen as striking at the very fundamentals of a paradigm and yet persistently resists attempts by the members of the normal scientific community to remove it. Kuhn cites as an example problems a.s.sociated with the ether and the earth's motion relative to it in Maxwell's electromagnetic theory, towards the end of the nineteenth century. A less-technical example would be the problems that comets posed for the ordered and full Aristotelian cosmos of interconnected crystalline spheres. Anomalies are also regarded as serious if they are important with respect to some pressing social need. The problems that beset Ptolemaic astronomy were pressing ones in the light of the need for calendar reform at the time of Copernicus. Also bearing on the seriousness of an anomaly will be the length of time that it resists attempts to remove it. The number of serious anomalies is a further factor influencing the onset of a crisis.