Have you ever been seduced by an argument? Watched it unfold before you, smoothly and softly, tugging you a little deeper with each sentence. For me, it was the gravity of ethicist Peter Singer’s proposition in Animal Liberation, written over 30 years ago, that drew me in: namely, that if animals are sentient beings just as we are, they probably want to avoid pain, just as we do.

It sounds simple, even obvious – and, on one level, it is. On another level, the complexities and subtleties are enough to occupy a lifetime of thought. It is a great paradox that part of what makes us human is the ability to disassociate our beliefs from our actions and our sense of self from the context that helped create us.

There is one thing I do know. It always begins with the same questifon. ‘Do animals suffer?’ The answer must be yes, so then comes the real question, namely can we then justify causing that pain?

The approach doesn’t lead to a conclusion but a string of questions, doubts and dilemmas. It is easy to see how so many of us simply give up.

Nevertheless, the animal rights movement has been gaining momentum for at least the last three decades. Soon-to-be-enacted reforms to New Zealand law suggest that the shift in public sentiment strongly favours a formal recognition of animal sentience. NZ legislators have listened, providing a serious precedent for Australia to follow.

What is animal sentience? The proposed New Zealand law contains no definition. So, while it seems like a significant step forward, with far reaching implications on everything from factory farming to live export, it also lacks weight.

Peter Singer is clear that it is not necessarily enough to insert a legal clause without a defined meaning.

‘I think that judicial activism would be very slow,’ he says. ‘It is a tool for judges, but probably no more. In Germany and Austria there are laws prohibiting unnecessary killing. But of course the question you’re going to ask is what counts as “unnecessary” and the truth is that remains more or less unresolved.’

Without a definition of sentience, it is unlikely that the debate in New Zealand will even reach that point. Marcelo Rodriguez Ferrere, who lectures about animals and the law at the University of Otago, thinks that the hollowness in the laws mean they could quickly lose any significance at all.

‘I am really hesitant because without a definition of what sentience really means, I am afraid this is just window dressing,’ he argues. ‘The idea of sentience here is not linked to those who care for animals or how people act towards animals. I mean, to be perfectly honest, it is unclear how it has the power to change anything.’

The reading speech suggests that the amendment is a direct response to public sentiment. Many of the submissions called not just for a recognition of sentience, but the banning of factory farming and live exports, as well at outlawing hunting. But the reforms barely touch on these topics in practice.

‘You have really got to question whether or not the public sentiment has been registered by Parliament or whether it has just simply been outweighed by economic interests,’ Ferrere says.

This is the most significant roadblock faced by the animal rights movement. Economically, most Western societies are built on the use of animals. Everything about the lives of many species of animals that no longer exist in the wild is dictated by commercial interest. Their very existence is predicated on the market demand for them. For this reason, assigning them rights, as we understand the concept, is counter-intuitive – if giving animals a right to move freely, breed freely and live with autonomy makes farming too expensive to be viable, it is conceivable that the species would no longer exist outside of zoos.

Instead, the law favours the idea of giving animals ‘freedoms’. In New Zealand, these freedoms are enshrined in legislation. But they are not widely enforced – the government outsources regulation to a not-for-profit organisation that is strained for staff.

‘We have very few inspectors actually categorising and cataloguing the breaches of the act, very few prosecutions. It’s deplorable, really, to encourage a poor attitude to animal welfare simply because there are no real consequences for not upholding it,’ says Ferrere.

Using animals while recognising them as sentient beings creates a difficult position to defend. But it is not an impossible view. Singer adds, if there is no real harm then there is no real problem.

‘You would have to show some actual harm to the animal, or I have a tough time finding it is truly exploitation,’ he says.

It all turns on definition, on drawing a line between exploitation and interaction, between using and abusing. Zoos, in particular, can fall on either side of that line. The central point is how humans view themselves in relation to animals.

Anthropologist and author of Only The Animals Ceridwen Dovey has long been interested in this use of animals.

‘I think sentience is a very important and very interesting turn,’ Dovey says. ‘When I was writing I was very aware that mine were very human animals. I think it was John Berger who said that “animals are the original metaphor”. They gave us the great gift of metaphor and over time we degraded them in language.’

Language, it can be argued, is one of the most important things separating ‘us’ from ‘them’. Humans first draw a distinction between species, and then use it to justify appropriating them both physically and in metaphor.

‘I was very wary of putting words in animals’ mouths. The only thing animals have left to confront us with is their silence,’ Dovey says of writing Only The Animals.

While researching the ethical boundaries of what defines humans as a species threw up new perspective on animals, but not in a traditional way.

‘I haven’t become a vegetarian,’ Dovey says. ‘I think everyone is very confused.’

Lurking beneath the surface of recognising sentience is an element of wanting to take humans out of the natural world, wanting to remove a sense of violence that would ordinarily occur. According to Dovey, this is a view that the current animal moment in literature is still coming to terms with.

‘In a way it has retired to folklore,’ she says. ‘If you look at the old traditions of the folk tale there is a darkness, there is the idea of an intense gaze you would get back from a wild animal that you wouldn’t get from an animal in a zoo … You don’t want to idolise that too much because that violence in the wild reminds you that life is meaningless, and that our life ends with as little meaning of those species around us.’

Perhaps the driving force behind the recognition of sentience is the attempt to escape our own animal instincts. But, if we accept that animals feel, and then further accept that a distinction between their pain and ours is an arbitrary one, it seems our decision really comes down to whether we can justify treating species differently.

According to Ferrere, once you outline this approach many people alter their behavior as a result.

‘Public pressure is what has given rise to all of the changes so far,’ he says. ‘People find it very difficult to resist.’