|A generalized image of the combustion of wood (CxHy) reacting with oxygen (O2) in the air to produce CO2, H2O, and heat or fire.|
The first so-called "flux and fire" philosopher was Heraclitus, who theorized that fire was the primary element and that change was the underlying mechanism of all.
Theories behind the operation or mechanisms that occur in fire, specifically fire seen as one of the four classical elements (350BC), sulphur (1524), terra pinguis (1669), phlogiston (1703), caloric (1787), entropy (1865), led to the development of the science of thermodynamics. The traditional alchemical symbol for fire was the capital delta Δ.
The following are related quotes:
“The mind is not a vessel to be filled but a fire to be kindled.”
“Doubt the stars are fire. Doubt that the sun moves. Doubt truth be a liar. But never doubt I love.”— William Shakespeare (c.1600) (Ѻ)
“Someday, after mastering winds, the waves, the tides and gravity, we shall harness the energies of love, and then, for a second time in the history of the world, man will have discovered fire.”— Pierre Teilhard (c.1932), Toward the Future (pdf) (Ѻ); his mist widely-quoted statement, supposedly (Ѻ)
“When, as I have done on many occasions, one asks educated persons and even eminent scientists, ‘What is fire?’, one receives vague or tautological answers which unconsciously repeat the most ancient and fanciful philosophical theories.”— Gaston Bachelard (1938), The Psychoanalysis of Fire 
“In everyone’s life, at some time, our inner fire goes out. It is ithen burst into flame by an encounter with another human.”— Albert Schweitzer (c.1940) (Ѻ)
● Reflections on the Motive Power of Fire
1. Bachelard, Gaston. (1938). The Psychoanalysis of Fire (pgs. 2-3). Librairie Gallimard.
● Sestak, J. and Mackenzie, R.C. (2001). “The Fire/Heat Concept and its Journey from Prehistoric Time into the Third Millennium” (abs), Journal of Thermal Analysis and Calorimetry, 64: 129-47.
● Newton, David E. (2002). Encyclopedia of Fire. Oryx Press.
● Fire – Wikipedia.