The simple truth is that marriage isn't always about love, and love isn't always about marriage. There are lots of cases where people enter into arranged marriages, without there ever being any sense of love when they marry. There are also people who love each other deeply who never intend to marry. This is as true for gay and lesbians couples as it is for heterosexual couples.

But the real problem is when we say that all love is equal.

Same-sex marriage proponents say that polygamy shouldn't be allowed because marriage should just be about two people. But those who argue for polygamy rightly say that restricting marriage to just two people is as arbitrary as restricting it to only marriages between men and women, something same sex marriage proponents reject.

I can speak on the subject of polygamy with some degree of understanding. My Chinese grandfather had two wives at the same time, although only one - my grandmother - was allowed into Australia. It was only after my grandmother's death that my "second grandmother" was able to migrate to Australia. It has touched my extended family deeply.

Whilst I honour and love my grandfather deeply, what he did was selfish and unfair on those subsequent generations who have had to live with the consequences. My family is proof that love alone is not sufficient justification for marriage.

Around the world, polygamy is accepted in 58 countries; far more than allow sex marriage. It is even practised in our near neighbours of Indonesia, Singapore, Malaysia and the Philippines. I can confidently predict that if we allow same sex marriage then there will eventually be a demand that polygamy be legalised too. Do we really want that?

It doesn't end there. There are other relationships which would also demand legalisation. At present, it is illegal for a step-brother and a step-sister to have a sexual relationship - let alone marry - even though they have no blood connection. The same applies to a foster-brother and a foster-sister. If marriage is all about love, shouldn't these people also be allowed to marry too?

If the current debate was all about love, and only love, there wouldn't be a debate. The reason there is a debate is that a change to the marriage laws will fundamentally alter the shape of Australian society, and decent Australians have a right to be concerned at what may ultimately eventuate.

That is why, like millions of other Australians, I shall be voting ???no'.

Bill O'Chee is a former Nationals Party senator for Queensland. He served in the Senate from 1990 to 1999.