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Our fifth assignment requires us to examine the subject of scientific realism. This is the philosophical view that the world around us exists independently of our perceptions of it, and that accepted scientific theories provide an accurate, or at least mostly accurate, description of that world. We are asked to answer a number of questions on the subject with reference to the work of Thomas Kuhn1, Arthur Eddington2, James Ladyman3, and Hilary Putnam4. I have also included one of the questions from assignment one on Ladyman's work (on the difference between appearance and reality) which I feel is a better fit with the subject matter covered here. The questions, together with my answers, are listed below:
Explain why Kuhn held that the relationship between pre- and post-revolutionary science is characterized by incommensurability.
"Kuhn's interest in and study of the Copernican Revolution and other periods of revolutionary change in the history of science (which are interspersed with periods of what he calls normal science) led him to the belief that a paradigm shift typically involves the complete abandonment of existing theories in favour of new ones rather than a process if incremental change.
This is accompanied by the adoption of a new paradigm in which what he calls the disciplinary matrix – i.e. the framework within which the scientific activities take place – will be very different from that of the paradigm that has been replaced. This will usually include the terms of reference used, the methods used to carry out experiments, the kind of evidence that will be accepted in confirmation of the theory, the exemplars used, and many other attributes of the matrix. Even the meanings of previously well-understood terms relating to the field of scientific endeavour may be different in a post-revolutionary paradigm.
Kuhn maintains that it is therefore simply not possible to compare the characteristics of pre- and post-revolutionary science because, even though the theories involved deal with the same set of phenomena, they are formulated within radically different paradigms, using different parameters, terms of reference, and methods.
Simply put, the rules of the game will vary from one paradigm to another, and are dependent on the paradigm in place at a given time, in a given scientific community. There is simply little or no common ground to be found when trying to compare a new theory with its predecessor. This essentially explains his use of the term incommensurability, which means 'lack of common measure', to characterise the typical relationship that exists between successive theories.
Kuhn did backtrack somewhat in his later work to suggest 'a set of methodological criteria of theory appraisal' as Ladyman describes it, which can be applied to all scientific paradigms. However, these criteria are, by Kuhn's own admission, not a set of hard and fast rules, but more a set of values that can be applied to the process of theory choice. They are sufficiently general in nature as to be open to interpretation – so much so that the scientists applying them may still adopt opposing theories despite being able to legitimately claim that they have used a common methodology in arriving at their choice."
Why does Eddington say that he has two tables? What features serve to distinguish the two?
"Eddington uses a very ordinary object – a table – to illustrate the point that there are (at least) two ways of describing the world and the objects in it. The first way of describing the object depends on how the object appears to us, i.e. our perception of that object in accordance with our senses. We can see the table. It appears to be of a particular colour, size and shape. We can also feel it. It is solid and non-malleable. It has a certain weight. Eddington describes this version of the table as 'a commonplace object of the environment I call the world'.
The second way of describing the object is in scientific terms. This description is only possible thanks to what we know, or think we know, about the fundamental nature of material things. In this description, the table is (like most things in our scientific version of the world) mostly empty space. Within this void are the various charged particles (and presumably also a number of electrically neutral particles) which are rushing around at enormous speeds, and whose volume (by comparison with the table itself, as we perceive it) is negligible - a billionth of the bulk of the table itself, according to Eddington.
The distinction Eddington makes is between the world of common sense – a term which I assume he means uses almost literally – and the world as it is according to our best scientific theories. This suggests that what we are seeing is an illusion in some respects. Modern science has, according to Eddington, taken the true nature of reality further and further away from what we experience on a daily basis. Although the scientific table has its counterpart in the real world, he says, there is nothing in the real world that we can equate to things like charged particles. Eddington questions whether both versions of the table actually exist, and if so what the relationship between them is.
He outlines the idea of objects having two kinds of property. Primary properties are (sometimes unobservable) properties that things not only appear to have, but also have in reality, like length, breadth and mass. These properties exist whether we perceive them or not. Secondary properties are properties that things appear to have to an observer (but often don't have in reality), like colour or taste. The secondary properties are dependent on the primary properties (for example the colour of gold is due to its inner structure) but the opposite does not apply (not everything that looks and feels like gold, for example, is in fact gold).
Primary properties are measurable and quantifiable, or at least derivable from other primary properties, whereas secondary properties are not – they are simply a matter of perception. Thus, while it is possible to measure Eddington's table using the appropriate instrument in order to determine its length and breadth, its colour will be largely dependent on the lighting conditions prevailing when we observe it, and possibly on the state of the observer's eyes (they might after all be colour blind)."
What are the three fundamental requirements of scientific realism, according to Ladyman?
"Modern science postulates the existence of many entities that we cannot observe – at least directly. Scientific realism presents us with the view that we should accept that these entities exist, based upon what scientists tell us. According to Ladyman, scientific realism requires three kinds of what he calls 'philosophical commitment'. The first of these is the acceptance of the existence of a 'mind independent world of unobservable objects'.
The view that we can refer to, and say something about, the nature of such objects is called metaphysical realism. Mind-independence means that something exists, even if there is no-one around to perceive it as such. It is thus in what philosophers sometimes refer to as the external world; it does not exist only in the mind of an observer. Thus, both of Eddington's tables (the one that his senses tell him about and the one that is described by modern science as being mostly empty space in which charged particles are whizzing around) exist. The unobservable things (electrons, black holes, radio waves etc.) are part of Ladyman's mind-independent world of unobservable objects.
The second kind of philosophical commitment described by Ladyman is what he calls a 'semantic commitment to the literal interpretation of scientific theories and a correspondence theory of truth'. The first part of this essentially means making a commitment to take scientific theories literally, even the parts that refer to unobservable entities. This contrasts with the view of (for example) the logical positivists, many of whom took the view that observation and experience can be the only source of knowledge, and that unobservable entities (such as atoms and nuclear forces, for example) had no place in science.
Others took the view that such entities, though not to be taken literally, could be used as logical constructs to explain observed phenomena (semantic instrumentalism), or that they could be somehow explained in terms of observable phenomena (reductive empiricism). The second part (the correspondence theory of truth) is a commitment to the view that a statement is true if it corresponds to the facts.
The third and final philosophical commitment is 'an epistemological commitment to the claim that we can know that our best current theories are approximately true, and that they successfully refer to (most of) the unobservable entities they postulate, which do indeed exist'. My interpretation of this is that it implies a rejection of the view that we can only know about things that we can perceive or that can be directly construed from things we perceive, and can accept as knowledge scientific theories that consistently and accurately explain known phenomena, predict as yet unseen phenomena, and describe the unobservable entities that produce those phenomena."
Why, according to Ladyman, does scientific realism require both semantic and metaphysical realism?
"According to Ladyman, natural science is often considered to have replaced metaphysics as the means by which we try to understand the nature of things (what he calls the fundamental structure of reality). Science has however changed to the extent that many of the things we now claim to know concern things that we cannot observe, whereas classical science dealt with things that could be observed, or at least that could be explained in terms of things we can observe (one notable exception being gravitational attraction as it relates to Newton's theories, and which he always hoped to be able to one day offer a more satisfactory explanation for).
Direct realism (the view that there exist mind-independent objects which we can perceive directly through our senses) alone cannot account for unobservable entities. Furthermore, it does not always allow us to see the true nature of things (Eddington's table only looks brown under certain lighting conditions, for example), and sometimes gives us a false perception of things (for example, a pencil looks bent when partially immersed in a glass of water). Metaphysical realism is not subject to the same restrictions, and stipulates only that we must be able to say something about the mind-independent world (i.e. the 'external world') that is true, whether we can observe it or not.
Semantic realism (the view that what science tells us about the mind-independent world should be taken literally and considered to be true, even when it relates to entities that we cannot observe) is required because so much of what modern science tells us concerns unobservable entities. Indeed, we rely on science to tell us the nature of such entities, since we cannot directly observe them through our senses.
According to Ladyman, a combination of metaphysical and semantic realism (together with the epistemic requirement that scientific truths are knowable, that we know some of them, and that scientific terms successfully refer to things in the world) is required in order to provide us with the essential elements of what he calls standard scientific realism. It allows for the existence of the kind of unobservable entities that modern science describes, independently of our minds and the knowledge gained through our perceptions. This is a metaphysical requirement.
We are also required to accept that scientific statements about the world are assertoric (i.e. they genuinely assert something about the world and are thus capable of being either true or false), that they are irreducible (they cannot be otherwise expressed in terms of observable entities), and that the truth or falsity of such statements depend on conditions that can be determined objectively (in other words, that we can show that the statements correspond to or contradict what we already know about the world). These are the semantic requirements."
State, in your own words, Putnam's 'no-miracles' argument for scientific realism. Do you find it convincing? Why or why not?
"Putnam describes two kinds of argument in favour of scientific realism (the view that we should believe what our scientists tell us because it offers the best explanation of observable phenomena). These arguments are loosely classified as positive and negative. The negative arguments seem to rely on discrediting the alternatives to scientific realism.
The main positive argument, according to Putnam, is that realism is the only approach to science that does not require a scientific achievement, or the success of science in general, to be looked upon as miraculous. Realists claim that scientific theories are successful simply because they are true. Or at least, that this is the most plausible explanation for their success.
My understanding of Putnam's 'no-miracles' argument is that, if a successful scientific theory were in fact not correct, then its success could surely be seen as being somewhat miraculous. If, for example, our theories about the behaviour of electrons in semiconductor materials when a current is applied to them were incorrect in any of their particulars, then surely some evidence of this would have emerged by now. At the present time there are literally billions of electronic devices in use around the world whose operation relies on semiconductor technology.
I tend to agree with Putnam. Consider the fact that most people in the western world can now buy a computer, for less than a week's wages, that is thousands of times more powerful than the computer that put a man on the Moon (assuming you don't believe the conspiracy theories. . .) and only a fraction of the size. It would certainly be a miracle if this technology worked despite being based on a set of scientific theories that were not true, at least in their most important assumptions.
The same could be said about our theories concerning the propagation of electromagnetic waves (consider the ubiquitous mobile phone and the advent of the satellite TV networks), and many other modern technologies that we use daily but take largely for granted, all of which are based on scientific theories that deal with unobservable phenomena like electrons, electromagnetic waves, and so on."
As Ladyman (p. 17) points out, the difference between appearance and reality is central to metaphysics, and, by extension, science. Describe an instance where the two seem to come apart (from assignment one).
"The observation of a 'mirage' can occur under certain circumstances, for example in a desert, or anywhere else for that matter, if the right conditions exist. When a mirage occurs, the observer can see what appears to be a distant object somewhere it shouldn't be - maybe floating in mid-air, for example. There is of course a perfectly rational explanation for this type of phenomenon. A superior mirage is a particular type of mirage that occurs when some object or objects, out of line of sight below the distant horizon, is seen above the horizon.
This can occur when a relatively cool layer of air (perhaps over a body of water, for example) lies beneath a warmer layer of air. The different air temperatures mean that the lower (cooler) layer of air is denser than the higher (warmer) layer of air. As light coming from the object passes from one layer to the next, it is refracted (bent) because one part of the light wave changes velocity slightly ahead of the rest of the light wave, causing it to change direction.
Obviously with our modern understanding of the physics of light waves and how they behave when passing through the interface between transparent media of differing densities, the occurrence of a mirage is little more than a fascinating distraction. Before the nature of light was fully understood, however, this would have been a different matter. People living in cooler climates, for example, would rarely experience the conditions necessary to create this kind of effect. Most of the casually observed behaviour of light travelling through air in such regions would not have hinted at the possibility of mirages. The interpretation of such an occurrence would therefore most likely be supernatural in nature.
The following account is taken from 'Letters on Natural Magic' by Sir David Brewster, published by Chatto & Windus, Picadilly in 1883:
'. . . on the 23rd June, 1744, Daniel Stricket, who was then servant to Mr. Lancaster of Blake-hills (a place near Wilton Hall, and both of which places are only about half a mile from Souterfell), was walking, about seven o'clock in the evening, a little above the house, when he saw a troop of horsemen riding on Souterfell side in pretty close ranks, and at a brisk pace . . . The family was then summoned to the spot, and the phenomena were seen alike by them all. The equestrian figures seemed to come from the lowest parts of Souterfell and became visible at a place called Knott. They then advanced in regular troops along the side of the Fell, till they came opposite to Blakehills, when they went over the mountain, after describing a kind of curvilineal path . . . the view of them was not confined to the farm of Blakehills only, but they were seen by every person at every cottage within the distance of a mile, the number of persons who saw them amounting to about twenty-six. The attestation of these facts, signed by Lancaster and Stricket, bears the date of the 21st July, 1744.'
Brewster describes a number of other such occurrences, and later says this:
'The aerial troopers seen at Souterfell were produced by . . . unequal refraction from one side of the hill to the other. It is not our business to discover how a troop of soldiers came to be performing their evolutions on the other side of Souterfell; but if there was then no road along which they could be marching, it is highly probable that they were troops exercising among the hills in secret previous to the breaking out of the Rebellion in 1745.'
Many of the phenomena described by Brewster were, however, attributed to various supernatural causes by those having originally witnessed them."
Notes: