Falsifiable or Not

In his highly informative book, The Most Powerful Idea in the World, on steam and how it shaped the Industrial Revolution, William Rosen made an interesting point about a long-debunked theory of heat. Called the phlogiston theory, it said that anything hot had more of something inside it – the eponymous phlogiston – that would get released as it cooled.

The theory did seem to explain why what was left of the wood after burning (ashes) weighed less than the wood itself: because the phlogiston would have been released. But other observable phenomenon contradicted the theory:

-         Some substances (e.g. magnesium) became heavier after being burnt, contrary to what the theory predicted.

-         Other substances didn’t change weight even if they cooled e.g. a hot iron bar put in water weighed the same after it had cooled and was taken out of the water.

Here’s the part about the theory that Rosen found interesting:

“Though phlogiston theory is wrong, it is considerably more scientific than is generally understood.”

Huh? What’s so great about a theory that was ultimately proven wrong, you wonder? Why is Rosen calling it “more scientific than is generally understood”?

The answer: because the phlogiston theory was falsifiable. Let Wikipedia explain what “falsifiable” means:

“A statement is called falsifiable if it is possible to conceive of an observation or an argument which negates the statement in question.”

Falsifiability is a must-have characteristic of a scientific theory, as per the philosopher of science, Karl Popper. This may sound trivial until you think of fields that are not falsifiable. Like astrology. Is there any single observation that could refute astrology?

Any field that has a No answer to that question is not science, as per the principle of falsifiability. Rosen’s appreciation for the phlogiston theory was because it was falsifiable, a rare thing back then even for scientific theories.

P.S. (The lack of) Falsifiability is also the reason why many physicists don’t consider certain modern day theories like the multiverse theory to be science either.