Was the human soul the original architect of our body's internal chemistry?

Ideas & Philosophy · Published 3 October 2026 Swipe more like this →

In short: Georg Ernst Stahl, a 17th-century physician, rejected the idea that life was merely a machine. He argued that a non-physical agent, the anima or soul, actively directed our biological processes. While his famous phlogiston theory was eventually debunked, his insistence on the soul's role shaped early modern medicine.

Born in 1659 in Ansbach, Georg Ernst Stahl was a German polymath whose work bridged the gap between alchemy and modern chemistry. Raised in a devout Pietist household, he grew to view the living body as fundamentally distinct from inanimate matter. While he acknowledged that physical components played a role in biology, he insisted that mechanical explanations alone could not account for the complexity of life. Instead, he proposed that an anima, or soul, acted as the primary governor of the organism.

Stahl’s medical philosophy centered on the concept of tonic motion—the rhythmic contraction and relaxation of tissues that facilitated circulation, secretion, and excretion. He believed the anima used these motions to prevent the natural decomposition of living tissue. This perspective put him at odds with the era's prominent iatro-mechanists, such as Hermann Boerhaave and Friedrich Hoffmann, who sought to explain health and disease through purely physical, materialist frameworks. His intellectual sparring with Gottfried Leibniz on these matters was even published in 1720.

In chemistry, Stahl is best remembered for the phlogiston theory, which he developed by expanding on the work of Johann Joachim Becher. He posited that combustible materials contained a substance called phlogiston, which escaped during burning, leaving behind a calx or ash. Although this theory was later overturned by Antoine-Laurent Lavoisier’s discoveries regarding oxidation, it served as a crucial unifying framework that encouraged empirical investigation. Stahl’s legacy remains a fascinating example of how vitalist concepts once provided a necessary structure for scientists to organize their observations before the advent of modern chemical and biological paradigms.

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