In alchemy, Paracelsus (1493-1541) was a Swiss physician noted for his early formulations of chemical affinity (Geoffroy's first law of affinity) and for his 1524 combination of Aristotle’s c.350 BC four element theory with Geber’s c.790 three principles. [1] The etymology of the word “gas” stems from Paracelsus’ used of the word khaos, in the occult sense of "proper elements of spirits" or "ultra-rarified water". [4]

On the topic of life, Paracelsus equated fire and life, in the logic that fire is life, and that whatever secrets fire truly bears the seed of life. [2]

Sulphur → Terra Pinguis → Phlogiston → Caloric → Entropy
In 1524, Paracelsusadopted Aristotle’s four element theory, but reasoned that they appeared in bodies as Geber’s three principles. Paracelsus saw these principles as fundamental, and justified them by recourse to the description of how wood burns in fire. Mercury included the cohesive principle, so that when it left in smoke the wood fell apart. Smoke represented the volatility (the mercury principle), the heat-giving flames represented flammability (sulphur), and the remnant ash represented solidity (salt). [3]

In 1669, German physician and chemist Johann Becher updated Paracelsus’ sulphur model of how things burn with a terra pinguis model of combustion, wherein terra pinguis was considered as the fatty, oily material substance of bodies that gives things the property of combustion.

In 1703, German chemist and physician Georg Stahl, one of Becher’s students, updated the terra pinguis model of with a phlogiston model of combustion. The deficiencies of this theory, as shown by experiment in later decades, led French chemist Antoine Lavoisier in the 1780s to develop the caloric theory of combustion. The deficiencies of this theory led German physicist Rudolf Clausius in the 1850s to develop an entropy model replacement for caloric and heat, which in turn gave birth to the science of thermodynamics (1865). [1]

See also
● Entropy formulations

References
1. Thims, Libb. (2007). Human Chemistry (Volume Two) (Paracelsus, pgs. 383, 426; Section: Heat and Affinity, pgs. 426-36) (preview), (Google books). Morrisville, NC: LuLu.
2. (a) Bachelard, Gaston. (1938). The Psychoanalysis of Fire (pg. 73). Librairie Gallimard.
(b) Fernández-Galiano, Luis and Carino, Gina (translator) (2000). Fire and Memory: On Architecture and Energy (pg. 266). MIT Press.
3. Strathern, Paul. (200). Mendeleyev’s Dream – the Quest for the Elements. New York: Berkley Books.
4. Gas – Online Etymology Dictionary.

External links
● Paracelsus – Wikipedia.