It is a form of promiscuity more opposed to conjugial love than the general type called simple adultery. It entails the loss of all ability and inclination for life in marriage, something Christians have from birth. These points can be proved by weighty arguments appealing to the reason of a wise person. As regards the first point, that having a concubine at the same time as or in association with a wife is a form of promiscuity more opposed to conjugial love than the general promiscuity called simple adultery, this can be seen from the following considerations. General promiscuity or simple adultery does not contain any love analogous to conjugial love, for it is merely a urge of the flesh, which immediately cools off, and sometimes leaves not so much as a trace of love for the woman, once it is over. Consequently this burst of wantonness does only a little damage to conjugial love, if it is not the result of deliberate or confirmed intention, and if the adulterer comes to his senses again.

The case of polygamous promiscuity is quite different. This contains a love analogous to conjugial love, for after bursting out it does not cool off, being dissipated and withering away to nothing like the first type, but it remains, renewing and establishing itself, making corresponding inroads on love for the wife and substituting coldness towards her instead. For he then looks on the woman who shares his bed as loveable, as the result of the freedom of will which allows him, if he will, to draw back, something implanted in the natural man; and because this is agreeable, it tends to support that love. Moreover with a concubine he is more closely attached to allurements than with a wife. On the other hand he looks on his wife as unlovable owing to the duty to live with her imposed by his compact for life, which then seems to him the more forced as compared with the freedom he has with the other woman. It is clear that his love for his wife cools off proportionately and she becomes despised, as his love for the other woman warms up and she is held dear.

[2] As regards the second point, that having a concubine at the same time as or in association with a wife causes a man to lose all ability and inclination for a life in marriage, something Christians have by birth, this can be seen from the following considerations. To the extent that love for a wife is transferred into love for a concubine, to that extent his love for his wife is eroded, emptied out and exhausted, as shown just above. This takes place by the shutting off of the inner levels of his natural mind, and the opening up of its lower levels. This can be established from the location of the inclination among Christians to love one of the other sex being at the inmost level; and the fact that this location can be blocked off, but not rooted out. The inclination to love one of the other sex, and also the ability to receive that love being implanted in Christians from birth, is due to that love which comes only from the Lord becoming a matter of religion; and in the Christian world the Lord's divinity is acknowledged and worshipped, and religion comes from His Word. That is why it is inherent, and why it is transplanted from one generation into the next.

We said that this Christian principle of marriage is destroyed by polygamous promiscuity; but this must be understood as meaning that in the case of a polygamous Christian it is shut off and intercepted. But it remains capable of being revived in his descendants, just as happens with the re-appearance of the likeness of a grandfather or great-grandfather in a grandson or great-grandson. That is why that principle of marriage is called the treasure of Christian life, and just above the jewel of human life and a treasure-house of Christian religion (457, 458).

[3] The destruction of the principle of marriage as the result of polygamous fornication in the case of a polygamous Christian who indulges in it is plainly to be seen from the fact that he cannot love his concubine and his wife equally, as a Mohammedan can. But the more he loves or has warm feelings for his concubine, the less he loves his wife or feels coldly towards her. An even more detestable result is that he is the more prone to acknowledge at heart the Lord as only a natural man and as Mary's son, and not at the same time as the Son of God, and to treat religion as worthless. Yet it must be well understood that this is what happens to those who take a concubine in addition to a wife, and have sexual relations with both of them. It does not apply to those who are separated for lawful, just and weighty reasons, and cut themselves off from sexual relations with their wives, but take another woman to enjoy in her place. This will be the subject of the next section.