Lost in Innovation: The Case of Phlogiston

post by adamShimi · 2023-01-20T12:19:00.603Z · LW · GW · 8 comments

This is a link post for https://epistemologicalvigilance.substack.com/p/lost-in-innovation-the-case-of-phlogiston

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Innovation and progress make the world a better place. They unlock new possibilities, correct past mistakes, and realize untapped potential. It’s not a coincidence that these words can have such positive connotations.

Yet to reap these benefits, progress must be carefully integrated into the old order. For innovators often turn their back on all that existed before, throwing away valuable past insights.

The best example I know of is the so-called Chemical Revolution at the end of the 18th century.

In most popular books and histories of science, this shift is presented as Lavoisier discovering oxygen, and with it the compositional approach to chemistry, replacing the old alchemy-imbued idea of phlogiston. The prevalent explanation of combustion at the time, phlogiston was a weightless fluid whose movement in and out of objects ruled combustion, respiration, and the properties of metals. But to the modern eye, it looks nothing like a scientific explanation — just a made-up fake substance, a fake explanation [? · GW]. It clearly couldn’t compete with Lavoisier’s composition of elements.

Or so we read in the modern treatment.^[1]

On the other hand, a quick look at our current best models of combustion (so called oxido-reduction reactions) reveal a weightless “fluid” whose movements capture the essence of the reaction: electrons. Sure, electrons are not a fluid; but they’re not really particles either according to quantum mechanics, and the fluid/substance frame fits with the concepts available at the end of the 18th century. Properties of metals also emerge from free electrons, confirming a key prediction of phlogistonist chemistry that Lavoisierian chemistry couldn’t explain.

Gilbert Lewis, of the Lewis diagram fame, makes this point in 1926 in The Anatomy of Science:

The phlogistonists were not content with the idea alone, but must add a mechanism, the hypothetical phlogiston, so that every process of the type we are discussing was supposed to involve the gain or the loss of this almost imponderable substance. By this mechanism they fell. They had not yet recognized that the air is a chemical reagent, and thought that the process of burning was merely the loss of phlogiston. When it was found that substances in burning gain in weight they were obliged to retreat before the proponents of the oxygen theory. If they had only thought to say “The substance burning gives up its phlogiston to, and then combines with, the oxygen of the air,” the phlogiston theory would never have fallen into disrepute. Indeed, it is curious now to note that not only their new classification but even their mechanism was essentially correct. It is only in the last few years that we have realized that every process that we call reduction or oxidation is the gain or loss of an almost imponderable substance, which we do not call phlogiston but electrons.

What is more, these key aspects of the modern treatment were completely removed by the Lavoisierian approach. There everything had to be explained in terms of composition. In adding this constraint, this strand of chemistry missed not only the key role played by electrons, but also most energetic considerations.

So Phlogistonists and Lavoisierian both only held one part of modern chemistry. As chemist William Odling wrote in 1876 in The Revived Theory of Phlogiston:

For most of what has since become known mankind are indebted to the surpassing genius of Lavoisier; but the truth which he established, alike with that which he subverted, is now recognizable as a partial truth only; and the merit of his generalization is now perceived to consist in its addition to—its demerit to consist in its supercession of—the not less grand generalization established by his scarcely-remembered predecessors.

[...]

The partial truth contributed by Lavoisier was indeed more wanted, more adapted to the needs of the time, than the partial truth which it displaced. To him chemists are indebted for their present conception of material _elements;_ and especially for their knowledge of the part played by the air in the phenomena of combustion, whereby oxygenated _compounds_ are produced. The phlogistians, indeed, were not unaware of the necessity of air to combustion, but, being ignorant of the nature of air, were necessarily ignorant of the functions which it fulfilled. To burn and throw off phlogiston being with them synonymous expressions, the air was conceived to act by somehow or other enabling the combustible to throw its phlogiston off; and a current of air was conceived to promote combustion by enabling the combustible to throw its phlogiston off more easily. Moreover, contact of air was not essential to combustion, provided there was present instead some substance, such as nitre, which, equally with or even more effectively than air, could enable the combustible to discharge itself of phlogiston. But, while the phlogistians, on the one hand, were unaware that the burnt product differed from the original combustible otherwise than as ice differs from water, by loss of energy, Lavoisier, on the other hand, disregarded the notion of energy, and showed that the burnt product included not only the stuff of the combustible, but also the stuff of the oxygen it had absorbed in the burning. But, as well observed by Dr. Crum-Brown, we now know "that no compound contains the substances from which it was produced, but that it contains them _minus_ something. We now know what this something is, and can give it the more appropriate name of potential energy; but there can be no doubt that this is what the chemists of the seventeenth century meant when they spoke of phlogiston."

Integrating the two perspectives is what modern chemistry does. Unfortunately, the Lavoisierian proved less sensible. Rather than looking for what phlogiston captured better than their new theory, they launched on of the most intense propaganda effort in the history of science, ensuring that for decades (and in most histories of chemistry to this day), no one could seriously invoke phlogistonian concepts and keep their scientific credibility.

They actually figured out a more satisfying form of modeling: where phlogiston was an unanalyzable substance, the Lavoisierian manipulated compositions whose structure and components could be investigated and amended. It’s obvious that phlogiston insights should have been integrated into the Lavoisierian model, not the other way around.

But blinded by their innovation, the Lavoisierian burned the whole history of combustion and salted the earth. In so doing they delayed the energetic and electronic understanding of chemistry by decades.

Here lies a lesson for champions of innovation: even though the point of progress comes in surpassing and replacing the past, we still must carefully integrate these new insights, or risk destroying hard won victories.

1. ^{^}

    The main exception I’m aware of is Hasok Chang’s Is water H2O?, which is the initial read that made me realize this historical bias and parts of its groundlessness.

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