Claim. Because God is incorporeal and invisible — even in the spirit-world — God’s intent was to take physical form through Adam and Eve, and the True Parents are that incarnation through which God can rule both worlds.
Elaboration. SMM makes the incarnational claim structural rather than mystical: “Since God is without physical form, He is invisible even in the spirit world. Consequently, God’s will is to become a parent with a physical body. By His becoming a parent with physical form, the incorporeal and the corporeal become one” (1.1. True Parents are the incarnation of God, 143-93, 1986.3.16). The mechanism is mature love-union: “Only in the presence of love will God attain a body that resembles His image. When Adam and Eve reach maturity as God’s physical body, God can dwell in their hearts and rule the physical and spirit worlds through them” (ibid). The claim escalates: “In the future, God will appear in the form of the True Parents in the spirit world” (ibid, 98-224, 1978.8.1). The doctrinal contrast with classical theism is sharp — divine incorporeality is reframed as a problem to be resolved through embodied true-love, not as a metaphysical perfection.
See also. csg-when-true-parents-enter-spirit-world-god-rules-through-them