NO one who has studied natural science, even in the most elementary way, can fail to be struck by the fact that one by one various theories have been put forward by human ingenuity to account for the relation and interaction of the constituents of the material universe and that one by one these theories have been discredited and destroyed by the light of discovery and experimental research. Paul was well aware of this when he said, "Whether there be tongues, they shall cease; whether there be knowledge, it shall vanish away."
Nothing, perhaps, better illustrates the unreliability of human theories and so-called knowledge, or science, than the history of what is known to chemistry as the phlogiston theory. This theory was enunciated at the commencement of the eighteenth century by Stahl, a doctor at the court of the King of Prussia, and was accepted with readiness by all scientific men; so much so, indeed, that it dominated and controlled all natural science for a period of half a century, and was in fact considered the basis of all scientific knowledge. Briefly, the theory was this: that all combustible bodies contained one and the same "principle" of combustion—phlogiston (from the Greek, phlogistos, inflammable). The escape of this phlogiston from a heated combustible body, becoming apparent to the physical senses on liberation, is called fire; or, to put it in another way, the phenomenon of fire is a manifestation of the imprisoned phlogiston escaping from its prison. The presence or absence of phlogiston was held to determine all the properties of bodies, to cause all the changes they were capable of expressing, to decide their color, taste, smell, and even their physiological and therapeutic value. The material phenomena of fermentation, decay, growth, and life-processes of plants and animals were all explained on the assumption that phlogiston was present in varying amounts or was absent entirely.
Now what truth or reality is there in the phlogistic theory according to the natural science of today? None, absolutely none! Physical scientists today know that there never was and never will be such a substance as phlogiston, for it never had any existence except as an illusion in the human mind; it was a false hypothesis from start to finish, and yet it was the paramount doctrine of the natural scientist for fifty years. Stahl and his followers certainly thought phlogiston was a definite substance, possessing all the essential attributes of matter, and that when isolated it would be found to be a solid, earthy body. Had a man in those days dared to stand up and say boldly, "There is no phlogiston," he would have been shouted down as an ignoramus, because he would have been opposed to all the learning of the day; he would have had no standing in the scientific world of thought.
