Attempts are made to give phenomenological reasons for nonlinear Casimir-Onsager reciprocal relations. The fluxes can be defined as time derivations of state variables, or they can be explained by means of balance equations, because only their vectorial properties are used. At first, time reversal is replaced by an abstract parameter reversal from which involutoric transformations of forces and fluxes result. The connection between the parameter reversal of forces and fluxes allows to give reasons for relations which are equal to the Casimir-Onsager reciprocal relations apart from a sign. This sign is determined by experience. The connection between parameter and time reversal is discussed.
The conditions sufficient for a phenomenological derivation of non-linear Casimir-Onsager reciprocal relations are restated and discussed. The main assumption is that systems can be combined without restriction. The time-reversal is identified with the parameter-inversion of the thermodynamical forces. In a supplement non-linear reciprocal relations are expanded in components, and their validity is shown for the non-linear case if the forces depend on each other.