"A general self-consistency approach allows for a thorough treatment of the corrections to the mean-field approximation (MFA). The natural extension of standard MFA with the help of a cumulant expansion leads to a point of view on the effective field 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 coarse-graining procedure. We outline and justify our method by some preliminary calculations. Results are given for the critical temperature and the Landau parameters of the ϕ4 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. A comprehensive description of the ground-state properties of many-body systems is also demonstrated."