“This we now say, that, according to this condition of being born and dying, which we know, and in which we have been created, the marriage of male and female is some good; the compact whereof divine Scripture so commends, as that neither is it allowed one put away by her husband to marry, so long as her husband lives: nor is it allowed one put away by his wife to marry another, unless she who have separated from him be dead. Therefore, concerning the good of marriage, which the Lord also confirmed in the Gospel, not only in that He forbade to put away a wife, save because of adultery [i.e. separation; not divorce or annulment], but also in that He came by invitation to a marriage, there is good ground to inquire for what reason it be a good. And this seems not to me to be merely on account of the begetting of children, but also on account of the natural society itself in a difference of sex. Otherwise it would not any longer be called marriage in the case of old persons, especially if either they had lost sons, or had given birth to none. But now in good, although aged, marriage, albeit there has withered away the glow of full age between male and female, yet there lives in full vigor the order of charity between husband and wife.” St. Augustine, “Of the Good of Marriage”, Par. 3