Thomas Aquinas

“ Wherefore affinity is not contracted except there be mingling of seeds, from which it is possible for carnal generation to follow. Now spiritual generation is not perfected except by a sacrament: wherefore it does not seem fitting for spiritual relationship to be contracted otherwise than through a sacrament. Hence others say that spiritual relationship is only contracted through three sacraments, namely catechism, Baptism and Confirmation, but these do not apparently know the meaning of what they say, since catechism is not a sacrament but a sacramental. ”

“ Reply to Objection 3: If the wife be not baptized, the spiritual relationship will not reach her, because she is not a fit subject, and not because spiritual relationship cannot pass from husband to wife through marriage. ”

“ Properly speaking a spiritual relationship is not contracted through the sacrament of Penance. Wherefore a priest's son can marry a woman whose confession the priest has heard, else in the whole parish he could not find a woman whom he could marry. ”

“ Further, the godfather and godmother have more in common in the spiritual birth that is the cause of spiritual relationship, than a husband, who is godfather, has with his wife. Now godfather and godmother do not hereby contract spiritual relationship. Therefore neither does a wife contract a spiritual relationship through her husband being godfather to someone. ”

“ From the fact that corporal and spiritual union differ generically we may conclude that the one is not the other, but not that the one cannot cause the other, since things of different genera sometimes cause one another either directly or indirectly. ”

“ In catechism one makes a profession of future Baptism, just as in betrothal one enters an engagement of future marriage. Wherefore just as in betrothal a certain kind of propinquity is contracted, so is there in catechism, whereby marriage is rendered at least unlawful, as some say ”

“ The addition of a person by carnal generation entails a degree with regard to a person connected by the same kind of relationship, but not with regard to one connected by another kind of relationship. ”