Having a concubine at the same time as or in association with a wife is polygamy, even if not recognised as such, because it has not been laid down and so named by any law. Anyone, even if not perspicacious, can see this. For the woman is like a wife used for enjoyment and a partner in the marriage bed. It was proved in the chapter on polygamy [XV] that this was condemned and to be banished from the Christian world, especially where it was shown that a Christian is not allowed to marry more than one wife (338); and that a Christian who marries several commits not only natural, but also spiritual adultery (339). This was allowable for the Israelite people, because the Christian church did not yet exist. (340). It is obvious from these considerations that having a concubine in addition to a wife and sharing a bed with either is foul polygamy.