Friday, May 25, 2018

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).

Monday, May 21, 2018

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.

Thursday, May 17, 2018

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).

Monday, May 14, 2018

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.

Friday, May 11, 2018

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.