  A general self-consistency approach allows a thorough treatment of the
corrections to the standard mean-field approximation (MFA). The natural
extension of standard MFA with the help of a cumulant expansion leads to a new
point of view on the MF theories. The proposed approach can be used for a
systematic treatment of fluctuation effects of various length scales and,
perhaps, for the development of a new coarse graining procedure. We outline and
justify our method by some preliminary calculations. Concrete results are given
for the critical temperature and the Landau parameters of the theory -- the
field counterpart of the Ising model. An important unresolved problem of the
modern theory of phase transitions -- the problem for the calculation of the
true critical temperature, is considered within the framework of the present
approach.
