A new method of approximation scheme, with potential of application to a general , interacting quantum theory is presented. The method is non-perturbative, self-consistent, systematically improvable and uniformly applicable for arbitrary strength of interaction. It thus overcomes the limitations of the existing methods, such as the perturbation theory, the variational method, the WKBJ method and other approximation schemes. The method has been successfully applied to a variety of interacting quantum systems including the anharmonic/ double well oscillators (with general quadratic-, quartic-, sextic- and octic couplings), the hydrogen atom and to the (lambda phi^4) quantum-field theory. The method yields important insight to the structure and stability of the physical vacuum. The results are shown to be consistent with the exact results predicted by supersymmetric quantum mechanics wherever applicable. Possible application to quantum statistics and finite temperature field theory is discussed.
