The article proposes a theory of a unified force field, based on the recognition of the inevitability of oscillations in the inhomogeneous density field of the "primary" form of matter ("prematter"), which was previously called ether. It is shown that the energy of these oscillations is equal to the product of the mass involved in this motion by the square of the speed of light, and the inhomogeneity of its distribution generates an all-pervading gravitational field proportional to the density gradient of the pre-matter. The corresponding short-range (field) form of the law of gravity is found, which reveals that gravity belongs to the most "strong" interactions and predicts the appearance of both attraction and repulsion forces in continuous media. Taking into account the pre-matter as an indispensable component of any material system in the law of conservation of energy allows us to consider the processes of its transformation into ordinary matter as a spontaneous phase transition in an isolated system such as the Universe as a whole. The most detailed form of the energy conservation law obtained on this basis predicts the existence of new types of interactions and new reciprocity relations between the intensities and impulses of various force fields. It follows from them that any force fields are a special case of the gravitational field and are generated by the uneven distribution of their energy carriers in space. This makes it possible to obtain a universal law of interaction, the strength of which is determined by the density gradient of the corresponding form of energy. This makes the pre-substance the true "fuel" of the Universe, and the gravitational field - the primary source of energy for all processes of the synthesis of matter in it. The similarity of the processes of transformation of various forms of energy is revealed and numerous examples are given that confirm the interconnection of fields and the possibility of creating new types of power plants based on field forms of energy.