Engines of Our Ingenuity

No. 1955:
STAHL, PHLOGISTON, AND ANIMA

by John H. Lienhard

Today, heat as substance. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

Georg Ernst Stahl was a curious fellow. A giant of early eighteenth-century science, he was born in Germany around 1660. He became a doctor and spent his life as an academic. He worked in chemistry, medicine, and philosophy. He's sometimes described as harsh and intolerant, but biographer Lester King thinks the evidence for that is flimsy. His personal motto tells us as much as anything can about his personality. Stahl said,

Where there is doubt,
whatever the greatest mass of opinion maintains ... is wrong.

Science had just undergone a great shift. A new experimental science was gaining its footing. We were starting to believe that matter is made of atoms instead of the old alchemical essences -- earth, air, fire, and water. Stahl fit into this ongoing scientific revolution in a very odd way.

Georg Ernst Stahl He was intensely religious, and he believed in a living anima, or soul. But his anima was a real force that impelled all motion within the body -- blood flows, secretions. He didn't like the way doctors were starting to analyze the body in terms of component parts and processes. You couldn't treat it piecemeal -- dismantle it like a watch -- because the anima inhabited the whole body. (Makes you wonder -- was he far ahead of his time or far behind?)

His belief in atoms is equally perplexing. The alchemist Johann Becher had claimed that only three alchemical essences formed matter: The salty earth, the sulfur earth, and the mercurial earth. These were more down-to-earth versions of the old "earth, fire, and water." Becher had taken air to be inert and irrelevant. Stahl adopted those ideas, but he believed the three earths, and air, were made of atoms -- and in constant motion.

So here's a lesson in how science changes: A century later we would finally accept a complete atomic description of matter. Until then, we kept bending the old science to fit new findings. Eventually enough evidence piled up, enough contradiction-laden Stahls did their work, and we finally saw everything through new eyes.

Take the question, "What's heat made of?" The Greek word for fire is φλογο (flogo); the word for fiery is φλογιστοσ (flogistos). So Stahl renamed the sulfur earth as phlogiston, and he described it in a new way. Phlogiston entered or left during any chemical reaction. And it could be stored in, or taken from, the atmosphere. Today, you hear people ridicule phlogiston. Yet how different is it from our talk about heating values of fuels? (Not much at all.)

So science is like a slowly leaking faucet. Water builds up at the exit, held in check by surface tension. Finally enough gathers to form a drop and break away. The breakaway is the exciting part -- water falling free, escaping. If we could spot that slow buildup as it takes place -- if we could recognize it along with all the Stahls among us -- we could predict the future, we could all get rich. ... And what would be the fun of that!

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


L. S. King, Stahl, Georg Ernst. Dictionary of Scientific Biography (C.C. Gilespie, ed.) (New York: Charles Scribner's Sons, 1975).

I am grateful to Stanley Reiser, University of Texas Medical Center, for his counsel.


phlogiston leaving an Oregon farm
In which an Oregon farmhouse loses its phlogiston. (Photo by John Lienhard)


The Engines of Our Ingenuity is Copyright © 1988-2004 by John H. Lienhard.