The Primary-Secondary Quality Distinction

This is another article (very lightly edited here) I wrote and posted on the Internet in 2009.

In the Appendix of the second edition of Introduction to Objectivist Epistemology Ayn Rand says the primary-secondary quality distinction (PSQD) is invalid. “The primary-secondary quality distinction is a long philosophical tradition which I deny totally. Because there isn't a single aspect, including length or spatial extension, which is perceived by us without means of perception. Everything we perceive is perceived by some means.” 

Of course, everything we perceive is perceived by some means, but the famous supporters of the PSQD, like Galileo Galilei and John Locke, did not deny this. Rand’s argument was against a straw man. 

Primary qualities are those of objects regarded as independent of any observer, such as solidity, extension, motion, number and figure (shape). They exist in the object self-contained and do not rely upon anything external. Secondary qualities are those that produce sensations in observers, such as color, taste, smell, and sound. A sensation or perception can differ due to different perceptual systems, e.g. color-blindness versus normal color vision, or what is external to the object, e.g. light conditions. The powers an object has to produce sensations in us depend on its primary qualities (John Locke, ECHU, II, VIII, 10). 

Rand says, “The primary-secondary distinction in fact starts from the idea that that which we perceive by some specific means is somehow not objective.” I disagree if “not objective” was intended to mean “subjective” in her vocabulary.  Using her intrinsic-objective-subjective trichotomy, the PSQD says that primary qualities are intrinsic rather than objective. Secondary qualities are objective in this regard. Indeed, next she says: “Now you can properly distinguish that which is in the object from the form in which you perceive that quality. But that isn't the same thing as saying color is a secondary quality but extension is a primary quality.” I agree it isn’t the “same thing”, but such distinguishing is what the PSQD does. 

In Objectivism: The Philosophy of Ayn Rand Leonard Peikoff says the dominant view by philosophers gives only two possibilities in regard to sensory qualities: they are "in the object" or "in the mind." The former is taken to mean qualities independent of man's means of perception; the latter is taken to mean "subjective and/or unreal." Why he says this view is dominant is beyond me, and it isn’t the case for the major supporters. More accurately, the PSQD does not say secondary qualities are solely "in the mind", but that they are not solely “in the object.” 

Locke went on to say that our ideas of primary qualities resemble those qualities as they are in an object, but that is not true of our ideas of secondary qualities. He stated this as a conclusion without further explanation (ECHU II, VIII, 9). He did not use what I regard as a strong argument for the PSQD.  That is the nature of our various senses, something Aristotle noted long ago. According to Aristotle the “common sensibles” are motion, rest, shape, magnitude, number, and unity (De Anima III.1 425a16). (Different translations might use slightly different terms here.) They are apprehended by more than one sense – sight and touch. For example, extension and roundness can be perceived by both sight and touch. What Aristotle called the “special perceptibles” were those grasped by one sense only, e.g. warmth, color, taste, smell and sound. Aristotle did not make the PSQD. He treated all qualities of an object or body as belonging solely to the object or body. However, he gave one of the means to do it. 

Another argument in favor of the PSQD is that primary qualities are measurable or countable, but secondary qualities are not. Measuring decibels or sound wave frequency or amplitude is not measuring the sensation of sound. Measuring light wave frequency or amplitude is not measuring the sensation of color. 

In The Evidence of the Senses David Kelley makes a PSQD, but not in the same manner and for the same reasons as Locke did.  Kelley says primary qualities are macroscopic and extensive, while secondary qualities are microscopic and intensive (p. 114-15, hb). This macroscopic-microscopic difference is not about the qualities of an object intrinsically; it is about our knowledge. Primary qualities as physical attributes exist at the microscopic level, too. “[W]e find that certain dimensions can be explained by reference to the macroscopic attributes of objects. With other dimensions, however, we cannot find the intrinsic feature of the object itself, to which the senses are responding, unless we proceed to the microscopic level” (p. 116).  It may be a bit clearer to the reader to substitute “features” for “dimensions.”  

"The perception of size, shape, position, motion, and number seems to require enough perceptual integration to isolate as units the objects which possess these attributes.  …  Thus it seems that the awareness of secondary qualities first occurs at the level of sensations, but the awareness of primary qualities require the perceptual level and necessarily includes some awareness of secondary qualities" (p. 113) “Moreover, since the primary qualities are macroscopic, it is easy to measure them as they are apart from the forms in which we perceive them” (p. 117).  

Kelley also makes an intrinsic–relational distinction between primary and secondary qualities (p. 110, 111, 117, 231). At times Rand described the relationship of consciousness to existence as “objective.”  

Rothbard on Economic Paradigms

Murray Rothbard made a succinct summary of Thomas Kuhn’s notion of paradigms and some interesting comments about it related to economic theory in his ‘Ludwig von Mises and the Paradigm of Our Age’ (here, also here).

Rothbard’s summary: Professor Kuhn provided a comprehensive model of the adoption and maintenance of scientific belief. He states that scientists adopt a fundamental vision or matrix of an explanatory theory, a vision that he calls a “paradigm.” And whatever it is, it governs all scientists in that field without being any longer tested or questioned, and further research comes from minor applications of the paradigm, clearing up loopholes or remaining anomalies. But gradually the anomalies pile up, and the paradigm weakens. Rather than being give up, patches and ad hoc adjustments are made. When the unresolved anomalies are big enough, a “crisis situation” is recognized, until it can be replaced by a new, comprehensive, competing theory that avoids or solves the pre-existing anomalies. It’s a “scientific revolution.” Even then, there remain those who hang on to the older theory, at least partly.

Without adopting Kuhn’s philosophical relativism, it becomes clear that intellectual vested interests play a more dominant role than open-minded testing, it may happen that a successor theory is less correct than a predecessor. If true, we must be open to the possibility that as discarded theories are forgotten and not looked at again, they may have contained scientific truth.

To whatever extent Kuhn’s thesis is correct about the physical sciences, where empirical and laboratory tests are obtained fairly easily, how much more it must be true in philosophy and the social sciences, where no such laboratory tests are possible.

Until recent decades, the classics of philosophy, political theory, and economics were read not just for antiquarian interest but for the truths that might lie there. The student of philosophy read Aristotle, Aquinas, or Kant not as an antiquarian game but to learn about answers to philosophical questions. It was not assumed that, as in physical sciences, all the contributions of past thinkers had been successively incorporated into the latest edition of the currently popular textbook, and it was therefore not assumed that it was far more important to read the latest journal article in the field than the classic works.

In recent decades the social sciences have been increasingly divorced from reality. They substitute statistics for experiment, abstract math, narrow specialties, writing technical minutiae for journals and not writing treatises characterize the discipline.

Rothbard continues, lamenting the effect on economics. “Of all the tragedies wrought by this collective amnesia in economics, the greatest loss to the world is the eclipse of the Austrian school.”

Scientific Revolutions #7

In The Rationality of Science W. H. Newton-Smith calls Thomas Kuhn a non-realist (ref. #6) because Kuhn's model of science makes problem solving the goal rather than the pursuit of truth. He says Kuhn doesn't make truthfulness the main goal of science because it cannot be given a rational justification. In other words, there is no algorithm for choosing which of two competing theories is better in all such comparisons. His exact words follow.

"Thus the use of models for the explanation of change is not the exclusive prerogative of the rationalist. Kuhn, for example, has a model of science which makes the goal problem solving and in which the principles of comparison are the five ways [ref. #5]. What makes Kuhn a non-rationalist is his thesis that these cannot be given an objective justification. This in no way precludes his using his model in generating minirat [*] accounts, a good example of which is found in his recent study of Planck. In this work, in which, interestingly, Kuhn does not make any use of his own theoretical framework of gestalt shifts between incommensurable paradigms, he explains why Planck opted for his distribution law for the radiation given off by a black body through a reconstruction of Plank's beliefs and reasoning processes. One example of a general methodological belief would cite as explaining the scientific community's acceptance of Planck's theory is the belief in the importance of theoretical unification. This, in part, motivated the community to prefer to use Planck's single formula which covers all temperatures instead of Wien's formula for low temperatures and the Rawleigh-Jeans law for high temperatures. ... This means that a rational representation of science should consist not of a single model but an evolving series of models " (p. 224-5). 

* minimal rational account -- an explanation of theory choice which does not include a normative assessment of the goal, or an evaluation of the truth or falsity, or the reasonableness or unreasonableness of the beliefs. 

I see no sharp difference between Newton-Smith's use of real and rational (and their conjugates).

Scientific Revolutions #6

Regardless of how one evaluates Thomas Kuhn's ideas about scientific revolutions, his book The Structure of Scientific Revolutions was a huge impetus in discussions of their nature. Commentary on the nature of science and scientific entities and methods preceded Kuhn's book, but the book spurred revisiting said nature, entities, methods, and scientific instruments.

Broadly speaking, scientific realism is the view that science is about reality. But there are significant nuances pertaining to truthfulness, aims versus achievements, mind-independence, what is or isn't knowledge, and more, including claims about unobservables (atoms, radio waves, etc.). This article Scientific Realism sketches the major nuances.

Antirealism is the term used for various arguments against, or foils for, scientific realism. One of these is instrumentalism, which holds that claims about unobservable things have no literal meaning. While the linked article doesn't mention Galileo and his religious detractors, it reminded me of them. Said detractors didn't object to some of Galileo's claims when viewed as instrumental, as mathematically useful. However, they did object to saying said claims were true when they conflicted with Biblical text.

Scientific Revolutions #5

In The Essential Tension Thomas Kuhn posits five characteristics of a good scientific theory to guide theory choice.

1. It should be accurate within its domain, that is, consequences deducible from a theory should be in demonstrated agreement with the results of existing experiments and observations.
2. It should be consistent, not only internally or with itself, but also with other currently accepted theories applicable to related aspects of nature.
3. It should have broad scope. Its consequences should extend far beyond the particular observations, laws, or sub-theories it was initially designed to explain.
4. It should be simple, bringing order to phenomena that in its absence would be individually isolated and, as a set, confused.
5. It should be fruitful of new research findings. That is, it should disclose new phenomena or relationships among those already known.

Kuhn adds: "Nevertheless, two sorts of difficulties are regularly encountered by the men who must use these criteria in choosing, say, between Ptolemy's astronomical theory and Copernicus's, between the oxygen and phlogiston theories of combustion, or between Newtonian mechanics and the quantum theory. Individually the criteria are imprecise: individuals may legitimately differ about their application to concrete cases. In addition, when deployed together, they repeatedly prove to conflict with one another; accuracy may, for example, dictate the choice of one theory or the choice of its competitor" (324).

In The Rationality of Science W. H. Newton-Smith presents his good-making features of theories as follows.

1. Observational nesting. A theory ought to preserve the observational successes of its predecessors. This is the primary indicator of increasing verisimilitude.
2. Fertility. A theory ought to provide scope for future development.
3. Track record. This fertility looking back. The longer the theory exists, the most important its track record.
4. Inter-theory support. That is, it supports other good theory and doesn't clashing with it.
5. Smoothness. Successful fine-tuning or corrections can be achieved in the face of failure.
6. Internal consistency.
7. Compatibility with well-grounded metaphysical beliefs.

He says many scientists and philosophers include simplicity as a good feature, but he discounts it because relative simplicity to a large extent lies in in the eyes of the theoretician and not in the theory. Quantum mechanics surely does not meet this criteria (226-31).

Scientific Revolutions #4

In addition to theories persisting -- by being modified but not eliminated -- some ideas persist even with revolutionary theory change. A good example is atoms. 

Realists have a simple explanation for this. The advocates were on the right track. They did not have the whole truth, but they had some of it. The idea that the physical world is comprised of atoms has persisted for centuries, even though ideas about the nature of those atoms has varied much with time. Even some prominent scientists in the 19th century thought atoms were only a useful fiction because they could not be directly measured. But more discoveries about atoms overcome the dissent. There must really be atoms, and we must really know something about them. Realists don't expect science always takes the direct road to truth and never deviates. But some ideas survive in spite of what develops. Indeed, these persistent ideas emerge stronger than before. Successful revolutions, though changing concepts in many ways, still have to accommodate those persistent ideas. (It Started With Copernicus, 186). 

On the other hand, some ideas are abandoned and support Kuhn's ideas of a theory meeting a crisis and being abandoned. A famous example is phlogiston. This was a substance thought to be released during combustion. There was considerable evidence to support the hypothesis, so it was a widely accepted chemical theory in the late 17th and much of the 18th century. So false theories can have true consequences, and go against the idea that science always converges toward truth.  The phlogiston theory was superseded by the oxygen theory of combustion.

Scientific Revolutions #3

The histories of science portrayed by Thomas Kuhn and Karl Popper -- according to their critics -- diverge from actual history. Parsons' counter-story follows.

"The history of science is not one of steady cumulative progress, but neither is it a succession of mutually exclusive paradigms where each new theory wipes the slate clean and starts all over again. If we regard all past theories as totally false, then the pessimistic metainduction probably should make us doubt our present theories, however empirically successful they are. But the history of science is not like the famous Peter Arno cartoon from the New Yorker: A test flight has just ended in a horrendous crash. The aircraft designer turns his back on the ensuing chaos, [and blithely says], "Well, back to the old drawing board." Science does not have to go back to the old drawing board with every superseded theory. Rather, when we look at the history of any field of science, a few theories will stand out as major breakthroughs. Once these breakthroughs occur, they are retained, in one form or another, through all subsequent theory changes, even through major conceptual revolutions. For instance, the mathematician and physicist James Clerk Maxwell (1831-1879) formulated a small set of simple equations that explained all the diverse phenomena of electricity and magnetism. He concluded that electricity and magnetism were different aspects of the same force, electromagnetism, and that light is actually a form of electromagnetic radiation. Maxwell's Treatise on Electricity and Magnetism was published in 1873, well before the two major revolutions in twentieth-century physics, relativity and quantum mechanics.
     The revolutions of twentieth-century physics overthrew some of Maxwell's ideas. For instance, he thought that since light was a wave, it had to be carried by some medium, the "luminiferous ether," an idea rejected by subsequent theory. However, light is still regarded as electromagnetic radiation, and Maxwell's equations, in modified form, are still regarded as valid for a given range of electrical and magnetic phenomena. Likewise, Newton's famous law of universal gravitation is retained in physics as correctly applying to things not moving too fast and to gravitational forces that are not too strong. So, many of Maxwell's ideas, like Newton's, have survived the enormous conceptual upheavals of the relativity and quantum revolutions, revolutions that overthrew so many of the ideas of "classical" physics. Within limited contexts, Maxwell's and Newton's theories are just as valid as they ever were. Other breakthrough theories have shown similar staying power in other fields of science" (p. 183-4).

Scientific Revolutions #2

In chapter 3 of It Started With Copernicus Parsons takes a "walk on the wild side", about those who criticize the idea that science is a wholly rational pursuit of truth. The "wild side" refers to social constructivism and postmodernism.

He concludes that while science is far from perfect -- like any human enterprise -- there is still something left of science idealized. There is a physical world "out there," and we can know something about it. We can say that some things really just are so, and not mere artifacts of our percepts, concepts, and categories. Further, our observations of the physical world can be used to rigorously evaluate our theories, so that our theoretical beliefs are shaped and constrained by nature, and not merely like in politics, rhetorical manipulation, or ideology. Disinterested knowledge is really possible, and is, in fact, achieved far more often than cynics suppose.

Nevertheless, the critics have succeeded in disposing of what might be called the "passive spectator" stereotype of knowledge. As that story goes, once people started looking at nature rather than old books, scientific knowledge flowed into open scientific minds like water pouring into an empty bucket.

Scientific discovery requires active engagement, not just passive seeing. Galileo didn't just look through his telescope and report what he saw. He interpreted, theorized, speculated, measured, analyzed, and argued. Darwin did not go to the Galapagos Islands and suddenly awaken to the truth of evolution in a flash of obvious insight. His notebooks reveal a complex process of questioning, argument, and counterargument, with tentative conclusions drawn and then rejected or refined. Scientists do not just absorb a picture of the world; they create a picture and then do their best to see how accurate it is.

Scientific Revolutions #1

I intended to borrow Thomas Kuhn's The Structure of Scientific Revolutions from the library to read it again after several years. Then I saw It Started With Copernicus by Keith Parsons on the shelf and borrowed it instead.

Here is another article about Kuhn and his book. Published in 1962, it attracted much attention with its ideas of paradigm, normal science, and incommensurability, with different paradigms being incommensurable. Parsons states three kinds of incommensurability in Kuhn's book (Chapter 2). They are about standards, values, and meaning (or semantics).

Standards pertains to what constitutes good science. Parsons' first example is why versus how as it pertained to Newton's position on gravity. "Must a theory of motion explain the cause of the attractive motion between particles of matter, or may it simply note the existence of such forces? Newton's dynamics was widely rejected because, unlike both Aristotle's and Descartes's theories, it implied the latter answer to the question" (p. 59). Another example is from paleontology.

Competing paradigms may disagree in basic values. Each theory, even in terms of its own standards, will have its own successes and failures. Which theory should we value more, the successes of one or the successes of the other? Which is the greater liability, the failures of one theory or its rival? Should we regard the successes of a theory as outweighing its failures?

Competing paradigms may use different meanings for the same term, e.g., mass, time, or gravity. While these term may refer to the same phenomena in Newton' and Einstein's physical theories, they are not understood the same.

As the above links show, Kuhn's ideas received plenty of criticism. Parsons is a critic, too, but gives Kuhn some credit.