"The time evolution of systems involving chemical reactions and diffusion
is described by a set of coupled nonlinear partial differential equations. The
solution of such equations, once suitable initial and boundary conditions
are provided, is notoriously difficult. In general, there exists more than one
solution. It is here that thermodynamics singles out a special solution,
namely, that corresponding to the "thermodynamic branch".
When we permit the system to deviate from equilibrium, new solutions
may or may not replace the "thermodynamic branch". Distance from
thermodynamic equilibrium then becomes the natural parameter in discussing
the appearance of new types of solution."
Nicolis, Gregoire, and Ilya Prigogine. Self-organization in nonequilibrium systems. Vol. 191977. Wiley, New York, 1977.