We present a formalism of a scalar, classical, and time-independent field theory of the type proposed by Ferrell for the treatment of continuous phase transitions. The formalism is developed along lines similar to those of many-body theory. All physical quantities, e.g., susceptibility, correlation length, and free energy, are expressed as functionals of the two-point time-independent correlation function and the order parameter. This is done both in the ordered and in the disordered phase. We obtain renormalized equations and diagram expansions of all quantities and self-consistent approximation schemes arc presented. It is shown that near the transition temperature, which is defined within the theory, no weak coupling limit exists. The generalization to more complicated field symmetries is straight-forward.