Emil Brunner rightly asserts that
… monogamy is the only possible union of the sexes which does justice to the personal need for full community.
Hence, marriage (naturally between persons of the opposite sex) is societally significant as it serves as the foundation for all other proper communities. Where there is no community, there is no society.
But the basis of monogamous marriage cannot be ‘love’ (Eros) as that term is usually understood. Brunner continues a bit further on
Where marriage is based on love all is lost from the very outset.
But how can such a thing be asserted?
The lover cannot guarantee that his emotion of love will be either permanent or directed solely to the one person: such a marriage, because it is only possible as a hypothesis, is broken the moment it has been concluded; or rather, it never existed.
Our fascination with and addiction to ‘individualism’ is at the root of modern culture’s misunderstanding of the purpose and strength of marriage.
It is this subjective individualism, more than anything else, which has caused the present crisis in marriage.
Marriage, theologically understood, is community and the foundation-stone of all community. That is why it’s important, and that’s why it matters. Marriages based on commitment to the other are marriages that are biblical. Marriages entered into for the sake of self fulfillment or self satisfaction (or lust) are doomed and no marriage at all.
In short, marriages rooted in αγαπη are true marriages (and since αγαπη is rooted in God and given by God, only those marriages established by and in God qualify as true). Marriages, on the other hand, rooted in ερος, are rooted in self and since so, doomed to fail, doomed to be truly inauthentic.