N.Wells
Posts: 1836 Joined: Oct. 2005
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Quote | Absolutely every single fact that phlogiston or stable continent theory purported to explain remains a fact accommodated within the replacement theories. Every single correct logical implication is contained within subsequent theories. |
Hi, NoName.
Replacement of one theory by another is a really interesting topic, and it is certainly true that there are many cases of new theories subsuming previous theories. The combination of electricity and magnetism into Maxwell's theory of electromagnetism is a classic example. The incorporation of genetics into Darwinian theory to make the NeoDarwinian Synthesis is another. However, I am unsure that this is true for the demise of phlogiston theory.
Phlogiston theory was 180 degrees wrong, and bought into the existence of a substance that didn't exist, so it was utterly refuted. Phlogistons were supposed to be an undetectable substance that was released into the air during burning. To some degree, phlogistons are anti-oxygen and "dephlogistication" (combustion) is oxidation, so whatever is said about phlogistication can sort of sound like a reversed description of oxidation, which could support a claim of phlogiston theory being subsumed into the caloric theory of combustion. We can sort of say that the facts of combustion, oxidation/reduction, and "calcination" sort of made it through the transition into the new paradigm, but in reality some were barely and mostly improperly understood as facts beforehand (oxidation and reduction), and others became obsolete afterward (calcination). So I think "tossed out in its entirety" is a better description of what happened. The ability of a substance to burn was supposed to be due to its phlogiston content: more phlogistons, more fire. However, air supposedly can't take up many phlogistons, so a candle burning in a closed bell-jar snuffs out when the air becomes saturated with phlogistons. Loss of mass on burning was ascribed to loss of phlogistons (rather than loss of CO2 and gain of O2). Charcoal leaves no ash because it is supposedly nearly pure phlogiston: some metal ashes can be turned back into metals when heated with charcoal (burned with a reducing flame) because the charcoal restores the levels of phlogistons in the ash. Breathing was considered to be the process of removing phlogistons from the body.
Lavoisier showed that some substances such as magnesium and also phosphorus and sulphur gain mass when they burn, despite supposedly losing phlogiston, which led some pro-phlogiston chemists to suggest that phlogistons had negative mass. Lavoisier also showed that that combustion requires a gas (later identified as oxygen) that has mass which can be measured by means of carefully weighing closed vessels, that metal oxides (then called calyces, like calyx of mercury) release oxygen when reduced, and that water could be formed from combining oxygen and hydrogen. By carefully weighing materials and balancing masses, he developed stochiometry and moved chemistry from more of a philosophically-based alchemy (where phlogistons reigned) to more of a lab-bench science (where oxygen and oxidation/reduction reactions could be properly understood). Priestley had discovered oxygen, but called it "dephlogisticated air", while Lavoisier figured out that it was a gas, called it oxygen, and explained its reactions.
There's an interesting description of why people bought into phlogistons, at http://lesswrong.com/lw.........lw..... Elizer Yudkowsky says Quote | Of course, one didn't use phlogiston theory to predict the outcome of a chemical transformation. You looked at the result first, then you used phlogiston theory to explain it. It's not that phlogiston theorists predicted a flame would extinguish in a closed container; rather they lit a flame in a container, watched it go out, and then said, "The air must have become saturated with phlogiston." You couldn't even use phlogiston theory to say what you ought not to see; it could explain everything. This was an earlier age of science. For a long time, no one realized there was a problem. Fake explanations don't feel fake. That's what makes them dangerous. ......
It feels like an explanation. It's represented using the same cognitive data format. But the human mind does not automatically detect when a cause has an unconstraining arrow to its effect. Worse, thanks to hindsight bias, it may feel like the cause constrains the effect, when it was merely fitted to the effect. |
That makes it sound like people talked about phlogistons somewhat in the way that Gary talks about intelligence: it's an incantation that appears to him to be an explanation, without him seeing that his words are completely ungrounded.
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