Now before I get into this, I do want to make clear that Becher was no fool; he was a well-respected and successful physician, an important political theorist and one of the first to define and study chemistry. But just in case you go thinking he was a genius, I should also say that he was an alchemist who believed that, if he could just find the right material, he could make himself invisible.
Becher's explanation of fire and combustion was quite simple: stuff that burned was full of phlogiston. The wonderfully-named phlogiston (pronounced pretty much as it looks: flodge-iston) was the very substance of fire. When things burned it was because their phlogiston was escaping into the air.
Although the notion of phlogiston seems quite silly these days, it actually makes a great deal of sense. The science of chemistry was only just becoming separate and distinct from alchemy and the phlogiston explanation tallied with observable facts. Combustion and rusting had been correctly linked as different aspects of the same thing and experiments were devised to prove the existence of phlogiston. The theory of phlogiston remained the pre-eminent explanation of combustion and oxidation for well over a century. Even as it lost ground, many of it supporters still regarded phlogiston as a principle rather than a literal substance.
Many experiments were conducted to investigate the existence of phlogiston and a lot of them yielded results that did indeed appear to confirm it. The experiment below was devised by Joseph Priestly:
Mercuric oxide is heated and the effluent passes down the
pipe and into the cylinder, displacing the water. The gas
collected in the cylinder supports combustion better than air.
You might have been told how computers work. you might have been told that electricity flows through the circuits and chips and somehow makes it all go. This is obvious nonsense, but it's how we explain things to beginners so it's easier for them to grasp. It also sounds complicated enough that no one ever asks any questions after that kind of explanation. The real truth is that all electrical and electronic devices run on a substance known as magic smoke.
All wires, chips, etc are filled with magic smoke. When they are damaged, the magic smoke escapes and they stop working. Look at this wire. It's been damaged and the magic smoke is escaping. Soon it won't work any more. You know it makes sense.