Claim. SMM treats conjugal exclusivity as a Principle-of-Creation mandate, not a moral convention: horizontal love between husband and wife is structurally destroyed by sharing, whereas vertical parental love is enlarged by sharing. The asymmetry is not contingent on cultural mores — it follows from how horizontal love is constituted.
Elaboration. The principle is stated as a structural claim: “According to people’s original nature, they do not want their partner’s love for them to be divided. The completeness of the horizontal love relationship between husband and wife is destroyed if that love is shared; whereas, this is not so in the vertical love relationship between parent and child. This is because of the principle-of-creation, which mandates that the husband and wife attain absolute oneness in love” (4.2. Conjugal love cannot be fulfilled if it is shared with another person, 277-200, 1996.4.16).
A two-mind disposition is treated as a metaphysical defect: “Some men, when they see a pretty woman, wish that she were his wife, even if he has his own wife. Of such a man with two minds, we say that he has a thief’s disposition. Since it is Satan who started out with two minds, it is not wrong to call a man ‘Satan’ who has two minds” (ibid, Blessed Family-348).
The failure mode is also named: “Why do a husband and wife fight? It is because each of them tries to receive love from the other. … A family where everyone tries to receive love will be shattered, but a family where everyone tries to love others will not be shattered” (ibid, 36-75, 1970.11.15).
Significance: the strong UC stance on monogamy and against extramarital fantasy is not legalism layered on top of love; it is treated as the only way horizontal love can stably exist.
See also. csg-parental-love-expands-through-sharing-not-diminishes