Statement of principle
In concise form, the "principle of substance stability" states that:
"During the formation or self-assembly of the most thermodynamically stable structures at the highest hierarchical level (j), e.g., the supramolecular level, Nature, in accordance with the second law, spontaneously uses predominantly the least thermodynamically stable structures available from a given local part of the biological system, belonging to a lower level, i.e. molecular level (j-1), and incorporates these unstable structures into next higher level, i.e. supramolecular level (j)."
In short, the principle of substance stability argues that each subsystem of the biosphere evolves according to its thermodynamic tendency to seek a free energy minimum during each evolution cycle.
Atomic evolution viewpoint
In 1978, Gladyshev wrote “after the concluding stages of general evolution the concentration of free energy occurs not only owing to the growth of the chemical component G j-im (intermolecular) and higher order components, but also owing to the G-j at (atomic) component (as well as to other components not considered here).” In these early formulations of the principle of substance stability, Gladyshev understood, from the viewpoint of hierarchical thermodynamics, the importance of the atomic component (G j-at) for the understanding of direction of biological evolution. In application, american chemical engineer Libb Thims' 2005 molecular evolution table, according to Gladyshev, shows that the composition variation of chemical elements (atoms) during evolution that corresponds to “the principle of substance stability”. The same situation, according to Gladyshev, should be found with the variation of isotope concentration of elements during ontogenesis and phylogenesis. 
In the sphere of sociology, with reference to family ties and their relation to society, according to Gladyshev, the principle of substance stability operates in social hierarchies.  In a generalized social matrix, one can visualize the substance, considered as an elementary structure, of any “inside” social hierarchy being defined as an understructure hierarchy, e.g. a hierarchy of organisms, groups of organisms, etc.
To cite one example, the stronger the love and mutual understanding between a couple, i.e. the understructure hierarchy, the less time they spend “outside” the family, i.e. the “over-structure hierarchy”. Marriage partners in types of stable relationships will not have the desire or impetus to seek external interaction and bonding as compared to less stable couples. Furthermore, according to Gladyshev, the principle of substance stability corresponds with the well-known rules of maintenance of stabilities of parties, unions, states, and nations, as personified by the age-old social management custom of “divide and rule”, in which higher hierarchies have fewer but more powerful and stable members. 
Wealth hierarchies and country hierarchies
In human economic wealth hierarchies, where social class tends to be stratified, from lower class, middle class, upper class, to millionaires, to billionaires, the principle of substance may explain the movements between the hierarchies as well as movement of people between the hierarchies of countries. In America, for instance, 80 percent of millionaires are first-generation affluent, meaning that eight out of every ten millionaires in American came from a lower class or lower hierarchy. 
Moreover, this trend seems to extend through time. Over one-hundred years ago, for instance, in The American Economy, Stanley Lebergott reviews a study conducted in 1892 of 4,047 American millionaires. He reports that 84 percent “were nouveau riche, having reached the top without the benefit of inherited wealth.” Likewise, regarding ethnicity, and cross-latitudinal migrations of people between hierarchies of countries, it is found that majority of newly-made millionaires in the most stable or highest hierarchy country, i.e. the United States, came from one of the least stable or lowest hierarchy countries, namely Russia an economic system that recently fell-apart, as the table shown above indicates.  These trends can be understood in terms of movements of human molecules between stability hierarchies. 
1. Gladyshev, Georgi. (2007). "Leonhard Euler's Methods and Ideas Live in the Thermodynamic Hierarchical Theory of Biological Evolution." International Journal of Applied Mathematics and Statistics, Vol. 11, No. N07, Nov.
2. Gladyshev, Georgi, P. (1978). "On the Thermodynamics of Biological Evolution", Journal of Theoretical Biology, Vol. 75, Issue 4, Dec 21, pp. 425-441.
3. (a) Thims, Libb. (2007). Human Chemistry (Volume One), (preview). (ch. 5 "Molecular Evolution", table: pg 122). Morrisville, NC: LuLu.
(b) Molecular Evolution Table - Institute of Human Thermodynamics
4. Stanley, Thomas J. and Danko, William D. (1996). The Millionaire Next Door – the Surprising Secrets of America’s Wealth. New York: Pocket Books.
5. ibid (pg. 17)