Does gay marriage prove marriage matters?

Just over a century ago, the Anglo-French writer, Hilaire Belloc, declared himself "opposed to women voting as men vote. I call it immoral, because I think the bringing of one's women, one's mothers and sisters and wives into the political arena, disturbs the relations between the sexes."

The idea that extending the franchise to women would do serious and irreparable damage to the social fabric is a useful reminder that views once widely held can soon seem absurd. Today, anyone in a western democracy who attacked the place of women in politics would not be taken seriously.

Yet we should also recall that it was to be many years before women enjoyed the same political rights as men. But views did change and as resistance was overcome, society changed too. So who's to say the same thing won't happen with marriage?

Last week, the Tasmanian House of Assembly became the first in Australia to come out in support of gay marriage. The historic vote was passed with the support of both Labor and the Greens.

Tasmanian Greens leader, Nick McKim, has pledged to push for the legalization of same-sex marriage in the Apple Isle if the Federal government does not act "in a timely way".

Now pressure is building on the Gillard government to take note. In Canberra, the Greens are determined to introduce same-sex marriage in the current Parliament.

Their goal is to enshrine equality for gay and lesbian people in legislation. Since the Australian people are much more conservative than the so-called 'inner-city elites' often realize, the Greens are likely to face a big political challenge.

Nevertheless, the Greens' commitment to same-sex marriage has already accomplished something significant, though they probably don't realize this.

By promoting same-sex marriage, the Greens have obviously moved the debate about the nature of marriage closer to the top of the political agenda. This is just how progressive ideas considered 'crazy' in one generation become commonplace in the next.

However, the Greens have also unintentionally kick-started a larger conservative debate about the health of the institution of marriage.

The first aspect is well-understood. The second tends to be completely overlooked.

In order for gay marriage to become uncontroversial, we would first have to agree on what marriage actually is. This is the fault-line dividing marriage traditionalists and advocates of gay rights. Yet that kind of agreement seems some way off.