same-sex marriage is vital for three reasons: liberty, conscience and state power.
That's the argument of Liberal Democrat David Leyonhjelm who on Wednesday introduced a private senator's bill to allow same-sex marriage.
The bill would allow any Australian to marry regardless of "sex, sexual orientation and gender identity".
However, it also gives non-government religious and civil celebrants the right to refuse to marry same-sex couples.
The libertarian doesn't believe government should interfere in individual choices and freedoms, and also supports the medical use of marijuana and assisted suicide.
Banning same-sex marriage diminishes people's ability to make life plans and marriage equality keeps state power in check, he says.
"The state is a wonderful servant but a terrible master," he says.
"The state cannot discriminate, and if it does so, that is an abuse of power."
He claims Prime Minister Tony Abbott counselled him against introducing the bill because it would cause more trouble for the government.
The Abbott government is under fire over a series of blunders and unpopular budget measures.
Mr Abbott promised pre-election to empower his party room to decide whether the coalition has a conscience vote on same-sex marriage, and Senator Leyonhjelm believes there is enough support for that to occur.
But the prime minister wants the bill abandoned, rather than allow it to proceed after coalition MPs are allowed a conscience vote, Senator Leyonhjelm said.
Labor MPs already have a conscience vote on same-sex marriage.
Senator Leyonhjelm intends to drum up enough votes for the bill to pass before bringing it on for debate.
The Greens will vote for marriage equality and urged Mr Abbott to allow a conscience vote.
Australian Marriage Equality lists on its website 13 nations and numerous US states where same-sex marriages are allowed, plus several more countries and individual cities where they are recognised.
It says it's "embarrassing" that same-sex couples can marry in Utah - a predominantly Mormon state - and Oklahoma but not Australia.
Debate on the Freedom to Marry Bill was adjourned.