We now regard that kind of thinking as offensive. But non-human animals are still often treated as property, to be dispensed with as the owner sees fit.

As ABC's 7.30 recently revealed, some thoroughbreds are meeting a wretched death in a brutal knackery and ending up as dogmeat. In these cases, the racing industry's welfare codes and re-homing policies seem to count for little.

Yet the same Enlightment-era reasoning that produced our cherished concepts of human equality and human dignity can lead us to conclude that we have extensive obligations to other animals.

The utilitarian philosophy developed by Jeremy Bentham is grounded in the principle that the interests of all human beings are equal. Your happiness (or suffering) matters just as much to you as mine does to me and must therefore be given equal consideration.

Racism and slavery were inexcusable, he concluded, but he also went further. Our ethical responsibilities should extend to animals, because just like us, animals feel pain. "The question is not, 'can they reason'? Nor 'can they talk'?" Bentham wrote, "but, 'can they suffer'?"

Similarly, Peter Singer, who coined the term Animal Liberation 46 years ago, believes there can be little doubt that animals suffer. As he points out, their external behavioural signs - "writhing, yelping, or other forms of calling, attempts to avoid the source of pain, and many others" - are so similar to our own.

Anyone who watched 7.30's footage of racehorses being slaughtered would have difficulty disagreeing with his argument.

A rival philosophical tradition leads to similar conclusions from a different starting point.

Bentham's German contemporary, Immanuel Kant, is famous for formulating the "categorical imperative" - that we must always treat other people as ends in themselves, and never merely as a means to our own ends.

For Kant, the main reason for being kind to animals is that we should avoid demeaning ourselves. He saw cruelty to animals as "demoralising" in the sense that it dulls the crucial human capacity to recognise and share in the suffering of others.

The 7.30 footage of abattoir workers cursing and kicking dying horses underlines Kant's argument. How could it be possible to carry out such brutal work without shutting down your own moral reasoning and turning horses into despised objects?

The world's leading interpreter of Kantian thought, Harvard's Christine Korsgaard, takes Kant's argument further. In Fellow Creatures, she argues that his reasoning leads to the conclusion that we must regard animals, like humans, as ends in themselves. It follows that we can't use animals merely for our own purposes.

This goes to the heart of growing unease with horse racing, harness racing and greyhound racing, as well as industrial-scale agriculture, live animal exports and animal experimentation.

In all these cases, we are treating animals primarily as instruments of our own satisfaction, whether for pleasure, profit or the pursuit of knowledge.

New animal welfare legislation in the ACT recognises animals as sentient beings with the capacity to feel and perceive - beings that deserve to have "a life worth living." It makes clear that they should be free of hunger and thirst, free of discomfort, pain, injury or disease, free to express natural behaviour, and free of fear and distress.

Pet owners who fail to exercise their dogs or feed their cats are now liable for criminal prosecution.

The ACT laws reflect the continuing influence of Enlightenment philosophies on contemporary thinking, and it is impossible to square them with the practices in the racing industry exposed by 7.30.

In the hope that Australians will still gussy-up for the Melbourne Cup, have a flutter on the neddies or at least join a workplace sweep and watch the race that stops a nation, Racing Victoria has promised to ensure that retired racehorses will in future be euthanised by vets on farms rather than sent to a slaughterhouse and turned into pet food.

Ten per cent of the revenue from Melbourne Cup carnival ticket sales and 5 per cent of Victoria Racing Club membership fees will be used to help build an equine wellbeing fund expected to be worth $25 million over three years.

But the industry response prompts further questions.

What does it mean to be a "retired" racehorse? Presumably it means that the owners of the horse no longer believe it is worth their while spending money on feeding and caring for the animal because it is unlikely to generate enough prizemoney or return on bets to cover their costs.

This doesn't mean the horse is old (the average lifespan of a thoroughbred is about 25 years), just that it is past its use-by date for racing. This may happen early in a thoroughbred's short racing career because it is injured or fails to perform to expectations.

No doubt many owners, trainers, jockeys, race stewards and others love horses. But it is harder to accept, as Racing Victoria chief Brian Kruger claims, that no one in the industry "had any idea" that some thoroughbreds were ending up on the killing floor of low-grade abattoirs.

Anyone, racing enthusiast or not, who had given the matter a moment's thought should have reasoned that there was a question here waiting to be answered: what happens to the horses that no longer race, or those that never make it onto the track in the first place?

Horse racing raises ethical questions that have been with us for generations. They are not about to go away.