Victoria's million plus Catholics will be urged to campaign against gay marriage.
Church leaders driving the push say it would undermine family life and damage society.
Catholic Archbishop of Melbourne Dennis Hart and five other bishops will send out 80,000 letters this weekend asking parishioners to take a stand against proposed new laws and influence politicians' vote.
One bishop said the push was about protecting traditional marriage, and while today's discussion was on same-sex laws, "next it might be polygamy".
On what grounds is same-sex marriage being opposed? On the same two grounds that I have opposed same-sex marriage myself:
a) Same-sex marriage will necessarily redefine what marriage means.
b) Same-sex marriage endorses the creation of fatherless or motherless families
Archbishop Hart makes it clear that he opposes the redefinition of marriage in this part of his letter:
The Government cannot redefine the natural institution of marriage, a union between a man and a woman. The Government can regulate marriage, but this natural institution existed long before there were any governments. It cannot be changed at will.
The argument that same sex marriage supports marriage is wrong. The natural institution will not only be changed, it will be re-defined absolutely. It will become something different. Such a re-definition will undermine rather than support marriage.
What does he mean? At the moment, marriage is held to be a lifelong, exclusive union between two people. That definition of marriage arose in the context of heterosexual relationships. When a man and a woman are brought together in a relationship it is the bringing together of two distinct but complementary parts that can be conceived to form a complete entity. The male and the female fit together as part of the plan to bring new life into the world. Therefore, it makes sense to conceive of marriage as existing between two people.
Furthermore, as the union of male and female exists naturally to produce offspring, it leads to a culture of sustaining a family life across the generations. The orientation is to provide a stable family life - the continuity of a kinship unit - over a long period of time. So it makes sense to conceive of marriage as an exclusive and lifelong union.
But same sex marriage doesn't fit into this traditional, heterosexual definition of marriage. Same sex marriage doesn't fit together two distinct but complementary parts. So why then would same sex marriage necessarily be between two people? If two men can marry, then why not three? And if two men are marrying, why does it have to be lifelong or exclusive?
That's particularly true given that same sex marriage is being pushed according to a newer concept of what marriage means. The newer concept is that marriage is a ceremony to celebrate the love that people feel. Homosexuals can feel love, the argument goes, so why shouldn't they then be able to marry?
For instance, the lead letter in the Herald Sun today criticises the Church's position on this basis:
As a heterosexual Catholic, I am dumbfounded by the church's constant discrimination against homosexuals.
The Bible says we are made in God's image, so why should the church oppose same-sex love?
Surely, love is love regardless of who expresses that love?
The church needs to reform and live in the present day.
Patrick assumes that marriage is a public expression of love and that therefore there is no reason to exclude the love that homosexuals feel. But that is a very open-ended way to define marriage. If marriage is there as a public expression of love, then not only is same sex marriage permitted, but so too is polygamous marriage (if a man loves more than one woman, it would presumably be thought fitting for him to marry all of them).
(In theory the newer concept of marriage goes even further in allowing people to marry anyone or anything they love. As Kristor pointed out at The Orthosphere there are people who have chosen recently to marry a dog, a bridge and themselves. Yes, that seems ridiculous, but it is logically within the newer concept of marriage as a ceremony to mark what you happen to feel love for.)
And if marriage is a public expression of love, then what happens when that love falters? Does that mean, by definition, that the marriage is over? Is the newer definition of marriage really going to encourage stable, lifelong unions?
The second reason to oppose same sex marriage is that it give official sanction to families which are deliberately created without a father or a mother. Archbishop Hart writes in his letter:
Bringing new human life into the world is founded on the loving union in difference of male and female. Children are best nurtured by a mother and father.
This argument can be put more sharply. If you endorse same sex marriage, then you are effectively accepting as a man that you are unnecessary as a father within a family. Your family could function just as well without you there. If two women can marry as a basis of family formation, and you believe that is a perfectly fine thing to happen, then you are writing yourself out of a necessary role within family life.
And that is likely to have consequences. If women believe that their children are better off having their biological father around, then that is a powerful motivating factor for women to act to keep the biological family together. But if society "moves forward" by sending the message to women that a father is not necessary to a child, then the stability of the heterosexual family is further compromised.
Where does the public stand on all this? At the moment public opinion is evenly divided. There is a House of Representatives website which is taking submissions and a poll on two bills that would legalise same sex marriage; currently those in favour of same sex marriage are leading slightly with 54% and those against 46%. (You can vote and/or leave a brief submission here).