AbstractThe genuine variational principle of macroscopic dissipative continua is generalized to complex scalar fields in the universal form of GAUSSian type. The generalization makes it possible to extend the validity of the principle to the PS field of the non‐relativistic SCHRÖDINGERequation, and to certain types of non‐linear problems. Following MORSE's and FESHBACH's sequence of thoughtful ideas in reverse direction the fundamentals of an “abstract” transport theory, isomorphic with one‐particle quantum theory, are developed and the possibility of interpreting the quantum theory by classical models is discussed. On the basis of new arguments, the impossibility of interpreting quantum mechanics in terms of classical transport theories (hydrodynamical model, diffusional and stochastic models) is e