482.  III.  DUPLICATE ADULTERY IS THAT OF A HUSBAND WITH ANOTHER’S WIFE, OR OF A WIFE WITH ANOTHER’S HUSBAND.  This adultery is called duplicate, because it is committed by two, and on each side the marriage-covenant is violated; wherefore also it is twofold more grievous than the former.  It was said above, n. 480, that the conjugial love of one man with one wife, after engagement and covenant, unites their souls, and that such union is that very love in its origin; and that this origin is closed and stopped up by adultery, as the source and stream of a fountain.  That the souls of two unite themselves together, when love to the sex is confined to one of the sex, which is the case when a maiden engages herself wholly to a youth, and on the other hand a youth engages himself wholly to a maiden, is clearly manifest from this consideration, that the lives of both unite themselves, consequently their souls, because souls are the first principles of life.  This union of souls can only take place in monogamical marriages, or those of one man with one wife, but not in polygamical marriages, or those of one man with several wives; because in the latter case the love is divided, in the former it is united.  The reason why conjugial love in its supreme abode is spiritual, holy, and pure, is because the soul of every man from its origin is celestial; wherefore it receives influx immediately from the Lord, for it receives from him the marriage of love and wisdom, or of good and truth; and this influx makes him a man, and distinguishes him from the beasts.  From this union of souls, conjugial love, which is there in its spiritual sanctity and purity, flows down into the life of the whole body, and fills with blessed delights, so long as its channel remains open; which is the case with those who are made spiritual by the Lord.  That nothing but adultery closes and stops up this abode of conjugial love, thus its origin or fountain and its channel, is evident from the Lord’s words, that it is not lawful to put away a wife and marry another, except on account of adultery:  Matt. xix. 3-9; and also from what is said in the same passage, that he that marries her that is put away commits adultery, verse 9.  When therefore, as was said above, that pure and holy fountain is stopped up, it is clogged about with filthiness of sundry kinds, as a jewel with ordure, or bread with vomit; which things are altogether opposite to the purity and sanctity of that fountain, or of conjugial love:  from which opposition comes conjugial cold, and according to this cold is the lascivious voluptuousness of adulterous love, which consumes itself of its own accord.  The reason why this is an evil of sin is because the holy principle is covered and thereby its channel into the body is obstructed, and in the place thereof a profane principle succeeds, and its channel into the body is opened, whence a man from celestial becomes infernal.