Claim. A filial child without a horizontal relationship to True Parents has nowhere to channel that piety: filial virtue requires both the vertical (God) and horizontal (True Parents) parental relationship to function.
Elaboration. “Yet, however much one may become a filial child or loyal subject, without having a horizontal relationship with True Parents, it would serve no purpose. It is only when the True Parent becomes the horizontal Father on the horizontal level that the vertical Father appears. When the absolute minus appears, then the absolute plus comes looking for it” (CSG 14.7 §2, 177-347, 1988.5.22). The argument is that ordinary filial piety cannot complete the four-position-foundation alone — the absent horizontal Parent position has to be filled by a substantial True Parent figure on earth before the vertical God-relationship can manifest. The teaching therefore makes attendance to True Parents not an add-on but a structural prerequisite for filial piety to do its work.
See also. csg-attending-true-parents-confers-filial-qualification