Last weekend my sister got married. I was asked to say a few things on the topic of love.

I’ve been asked today to talk about love. And I’m honoured, but unqualified. At first I thought, easy. I love. I have loved. I’ve loved deeply, shallowly, intensely, fleetingly … I’m even well acquainted with its corollary, heartache. I know love.

Love is … Hmm. Let’s see. Love is … passionate attraction, emotional connection, trust and security. Lust? It’s just feelings, lots and lots of feelings. Good job, me. Nailed it.

So maybe defining love in any meaningful way is actually quite hard.

Popular culture’s obsessed with the topic, let’s let them handle it.

Love was the ‘beginning of everything’ for F. Scott Fitzgerald, and it was apparently all the Beatles ever needed. So we know it’s important.

But is it permanent? Hemingway famously said it was ‘Better to have lost and loved than never to have loved at all’.

Maybe love it about utility. Not very romantic, but it makes sense. Marriage was once purely transactional. Our notion of romantic love is really only a few hundred years old.

And humans are, after all, social animals. We need other people. Not even necessarily in a romantic sense, but definitely in terms of basic survival. Our ancestors would have scarcely made it out of the trees without being eaten had we not worked out ways of living and working together. Our existence as we know it ­– the luxuries of modern life – we owe it all to our species’ ability to work together.

Plato described justice as a state when people come together truly as one another’s partners and helpers. Maybe love is a pure form of justice.

Iris Murdoch said: ‘Love is the very difficult understanding that something other than yourself is real.’ And for Oscar Wilde: ‘You don’t love someone for their looks, or their clothes, or for their fancy car, but because they sing a song only you can hear.’

Maybe love is when the world has meaning.

Which all leads to only one conclusion: there is no absolute definition of love. No one can tell anyone else what love is because a love can only exist between those who are party to it. The definition is yours and no one else’s.

And it’s in that spirit that Kathleen and Ioanis have asked me to express, on this day when they celebrating their unique love, that it is their fervent wish for marriage equality to be a reality in our country. Because if modern marriage is no longer the transactions of property and power, if it is about the celebration of the love two people feel each other, why on Earth does someone’s gender matter.

So I’ll leave the last word to Antoine de Saint-Exuprey, author of the Little Prince:

‘Love does not consist of gazing at each other, but in looking outward together in the same direction.’