Thomas Aquinas

“ Error about a person's rank, as such, does not void a marriage, for the same reason as neither does error about a personal quality. If, however, the error about a person's rank or position amounts to an error about the person, it is an impediment to matrimony. Hence, if the woman consent directly to this particular person, her error about his rank does not void the marriage; but if she intend directly to consent to marry the king's son, whoever he may be, then, if another man than the king's son be brought to her, there is error about the person, and the marriage will be void. ”

“ An error of faith about matrimony is about things consequent upon matrimony, for instance on the question of its being a sacrament, or of its being lawful. Wherefore such error as these is no impediment to marriage, as neither does an error about baptism hinder a man from receiving the character, provided he intend to receive what the Church gives, although he believe it to be nothing. ”

“ For if a man were to strike his father with an iron rod thinking it to be of wood, he is not excused from sin wholly, although perhaps in part; but if a man were to strike his father, thinking to strike his son to correct him, he is wholly excused provided he take due care. Wherefore error, in order to void marriage, must needs be about the essentials of marriage. Now marriage includes two things, namely the two persons who are joined together, and the mutual power over one another wherein marriage consists. ”