Of the four ancient Elements--earth, air, water, and fire--only the first three are truly "things". Fire is a behavior of things; modern physics considers it as arising from forces. At its least dynamic, fire is heat, which is the subject of this note. More dramtic forms include flames and radiant heat. Flames convert things by reorganizing atoms from one molecule into another. Radiant heat moves about through the elctromagnetic field, rather than directly through the interaction of molecules,

To the ancients the world was wrought from earth, air, water, and fire. This is not a bad approximation if you cannot probe finer than a fleas feelers. The first three are solids, liquids and gasses, which a modern physicist sees as matter. And the fourth--fire--corresponds to what the physicist calls energy.