1715 : Popularization of Phlogiston Theory

Stahl popularized the idea of phlogiston, an immaterial substance that motivates combustion. It may be present to differing extents in different materials depending on their capacity for burning. The phlogiston theory, though relying upon a matter that is indiscernible to the senses and direct measurement, represented a milestone in the departure from the “occult” practices of alchemy, and encouraged empirical testing.