Every real being, save perhaps one, must be constituted by a real metaphysical composition or inner structure or complementary polarity of two correlative metaphysical co-principles within the unity of one being: namely, (1) an act of existence, by which it actually exists, is actively present in the universe of real beings; and (2) a limitting essence, by which it exists in this or that particular mode or manner of existing, as this or that particular being and not some other.