Excerpt from the Mathematical Universe by Max Tegmark.

Marriage, as an example of a paramount modern social institution, becomes the next subject of discussion. Campbell differentiates between marriage and love affairs and imparts some very lofty ideals to marriage, in contrast to love affairs, that he categorically states inevitably end in disappointment. True marriage, in Campbell's opinion, embodies a spiritual identity and invokes the image of an incarnate God. Campbell and Moyers agree, somewhat surprisingly, that the main objective of marriage is not the birth of children and the raising of families. They discard the concept of perpetuation of the human species as being the primary function of marriage and relegate this to a first stage. This first stage is followed by a second one where the offspring have departed into the world and only the couple is left. Campbell invokes the image of marriage as being an ordeal in which the ego is sacrificed to a relationship in which two have become one. This, he states, is a mythological image that embodies the sacrifice of the visible for a transcendent good. Campbell labels this stage of marriage as the alchemical stage.On the subject of the ritual of marriage, Campbell and Moyers complain that it has lost its force and has become a mere remnant of the original; they contend that the ritual that once conveyed an inner reality is now merely form.