
The standard definition, according to English chemical thermodynamicist Edward Guggenheim (1933), of what constitutes the differences between an unnatural process and a natural process, based on the Clausius inequality, for standard earth-bound systems. [1]

The standard definition, according to English chemical thermodynamicist Edward Guggenheim (1933), of what constitutes the differences between an unnatural process and a natural process, based on the Clausius inequality, for standard earth-bound systems. [1]

In science, unnatural or ‘what is unnatural’, as contrasted with natural, is defined by processes or reactions, for standard earth-bound systems, that meet the following criterion: [1]

dG > 0

This is called the Lewis inequality that are ‘thermodynamically impossible’, defined in 1923 by American physical chemist Gilbert Lewis, based on the various Gibbs inequalities, which he termed as a “universal rule” for freely reacting isothermal-isobaric processes (e.g. ones that occur between reacting humans). [2] In generalized form, what is natural for any system or body of the universe is defined or quantified those processes or reactions that meet the Clausius inequality (1856).

See also
● Natural science

Quotes
The following are related quotes:

“Contrary to popular belief, being alive is unnatural.”
— Michael Guillen (1995), Five Equations that Changed the World (pg. 6)

References
1. Guggenheim, Eduard, A. (1933). Modern Thermodynamics by the Methods of Willard Gibbs (pgs. 5, 17). London: Methuen & Co.
2. Lewis, Gilbert N. and Randall, Merle. (1923). Thermodynamics and the Free Energy of Chemical Substances (pg. 160). McGraw-Hill Book Co., Inc.

Further reading
● Ball, Philip. (2011). Unnatural: the Heretical Idea of Making People (pg. 3). Vintage Books.