There are few issues where public opinion has moved so significantly in my lifetime as has occurred on same-sex marriage.
When I first entered Parliament in 1996, being in a same-sex relationship was still a criminal act in Tasmania.
Try explaining that to a school-leaver these days. It would be like describing a foreign country or what it's like to live through a recession.
That's why one of the least credible arguments against the same-sex marriage postal plebiscite is that Australians aren't up for having a civilised debate.
If majorities shut down debates merely because they are exposed to views that make them uncomfortable, we wouldn't be where we are today in recognising same-sex couples.
Diverse views are important
Former High Court Justice Michael Kirby's words after decriminalisation in Tasmania two decades ago still ring true.
"The winning over of public opinion," he wrote, "involves education and persuasion of fellow citizens in all of their diversity. Whatever the issue, we should respect those who hold views different to ourselves. Some of the people who opposed homosexual law reform were not evil or bigoted."
On the other hand, it is worth remembering that as conservatives our job is not to reflexively oppose change, but ensure that it is not being imposed top down and retains the best parts of the old.
To paraphrase Edmund Burke, an institution without the means of some change is without the means of its conservation. Marriage is a conservative institution which has evolved over time. There have been 20 separate changes to the Australian Marriage Act since Menzies introduced the law in 1961.
The 20 changes demonstrate Australian civil marriage embodies the conservative tradition of institutions evolving.
Conservatives should be in favour
Reforms undertaken by conservative governments have always remained firmly within community views and have been carefully drafted to avoid unforeseen consequences.
In 2004, for instance, I was Assistant Treasurer when the Howard government ensured that all same-sex couples who lived together could receive superannuation benefits tax-free on the death of their partner.This overdue reform received overwhelming support in the Coalition party room.
This natural judiciousness is the main reason why the "slippery slope" arguments about what might happen after gay marriage is legalised are off the mark.
Australia is hardly the first country to consider this issue. Around 25 countries have legalised same-sex marriage. The UK, New Zealand and the US have legalised it and have suffered no diminutions in their ancient freedoms covering speech and religion.
Conservative governments have rightly sought to defend marriage as a bedrock of social stability and a keeper of our values. Tied to this notion is that traditional marriage is the preserve of children, having them, nurturing and raising the next generation.
But even that is no longer true. In February same-sex couples saw another historic milestone achieved, with South Australia becoming the last state to remove its ban on them adopting children, explicit recognition that gay couples can successfully parent and raise their children.
Strengthening marriage for all
According to the census, a quarter of lesbian couples have adopted children (although that figure is much smaller for gay male couples).
Far from "weakening" traditional marriage, the experience in other jurisdictions is including same-sex couple in marriage strengthens the institution and increases the marriage rate.
As Malcolm Turnbull put it eloquently the other day: "If a gay couple gets married … that doesn't threaten my marriage to Lucy which is nearly 38 years of marriage."
This vote is not so much a threat to marriage but a chance to be re-energised by it and the commitment of others.
Including same-sex couples in marriage will deliver stronger families and communities. We'll see more commitment and responsibility as everyone in our families and communities will be able to commit to the person they love.
For these reasons, I have changed my own views on the definition of marriage. Not only will I be voting in the postal plebiscite, I will be voting with a resounding "yes".
Helen Coonan is a patron of Liberals & Nationals for Yes and was Minister for Communications and Assistant Treasurer in the Howard Government. She sits on the board of Crown Resorts.