The Church views marriage as a unique relationship between a woman and a man.
Marriage is also a fundamental institution for all societies because of its importance in uniting spouses as potential parents and in providing for the upbringing of their children. It has therefore been understood as the union of a man and a woman in all cultures and religions until very recent times and is still so defined in international law and the law of most nations.
The recognition that marriage is between a man and a woman is not the assertion of bigotry, religious dogma or irrational tradition, but a recognition of human ecology. It does not preclude persons of the same sex entering into other legal relationships.
To insist that marriage is a relationship between a man and a woman is not a criticism of other kinds of relationships. By recognizing this particular type of relationship our community and its marriage laws do not unjustly discriminate against other relationships: rather, our community and its laws recognize the essential connections between male-female bonding and child-bearing, and between children and their natural parents. The Commonwealth has an interest in ensuring that children have the benefit of those connections.
Redefining marriage would deliberately create motherless or fatherless families, which would deprive children of at least one of their biological parents, and would put the preferences or interests of adults before the right and interests of children.
Consequences of change
The Church recognises that genderless marriage would have flow-on consequences, where essential roles like motherhood and fatherhood would likely be erased from the law to the detriment of children.
Will people of faith be compelled by law to be involved in activities or ceremonies that are contrary to their beliefs?
Will religious organisations or agencies continue to be free to employ staff who abide by the ethos of those organisations regarding marriage?
Will religious organisations or agencies be free to bid for government contracts or other funding without being forced to endorse same-sex marriage?
Will faith-based schools, with a responsibility to pass on the faith, be free to teach that marriage according to their religion is only between a woman and a man and be free to employ staff who support those teachings?
We have seen each of these freedoms challenged overseas where the definition of marriage has changed. ( In Australia too we have already seen Hobart Archbishop Julian Porteous taken to the state anti-discrimination commission for distributing a booklet explaining the long held Christian view of marriage, upon which societies through the ages have been built.)
The consequences of changing marriage are very real.
from Australian bishops