No other subject arouses the same passion as animals and their welfare, which is to say that none generates so much heat and so little light. And none, I think, is both so painful and so prone to hypocrisy. Do any of us really know what we think, or where we stand?

Some think they do. All week long protesters have been trying to prevent the export of live calves and sheep to the Continent (or "to Europe", as some papers revealingly put it) from Shoreham in West Sussex. The cargo got away, but only after 1,000 police officers had been brought in and £350,000 of public money had been spent. Even though the trade is legal, not many people can take pleasure in this use of scanty resources, especially when one thinks of the three dangerous escaped criminals not many miles away. The Royal Society for the Prevention of Cruelty to Animals is totally opposed to the export of live food animals, and the Labour Party proposes to ban it.

At the same time, animal welfare defenders are divided among themselves. At one end there are the respectable moderates of the RSPCA and Compassion in World Farming. Members of the latter have tried to organise peaceful demonstrations at Shoreham, but found themselves outpaced by violent extremists and, CWF's Joyce D'Silva says, hooligans who abused her own staff. She ended the stormy week by appealing to both demonstrators and transport operators to stay away from Shoreham.

Not all the protesters are violent. To the outside of the RSPCA and CWF (some of whose members eat meat) are non-violent vegetarians, and vegans who use no animal products at all. But to their outside in turn are the activists in the "animal liberation" groups who use, frankly, terrorist methods, have broken into farms and laboratories, have smashed lorries and have sent letter-bombs to scientists and ferry operators. One was recently given an exemplary 14-year sentence for his terrorism.

The movement for animal welfare is popular with young people, whose radicalism tends to be more green than red. And it is backed by a phalanx of philosophers who have advanced a new doctrine of animal welfare (with vegetarianism taken for granted) based on the premise of animal rights, rather than on humanitarian benevolence or pity. This theory may not yet have penetrated the consciousness of the wider public, but it has produced a fair weight of academic texts.

If "animal welfare" is a broad church, and if it is confused as to ends and means, so, too, are the rest of us confused. I recognise my own confusion. I eat meat, but am squeamish about the live export of calves (not to say the veal trade as a whole) andfactory farming (I search out eggs from small farms, though as much because they taste better than supermarket eggs as from higher motives of conscience). I detested the only bull fight I ever saw and shed no tears for the ending of otter-hunting. But Ifish, and find it hard to criticise fox-hunters.

The Sun has jumped on the anti-field sports bandwagon and cites the majority of British people who favour a ban on hunting. No doubt there is also a majority opposed to live export. But Sun readers must have helped dispose of a fair number of the 10 million or so turkeys slaughtered over the last month. And it is not easy to make a strictly logical case against the transportation of animals, assuming conditions are tolerable, if one has no objection to their slaughter.

There are evasions, hypocrisies and contradictions on the animal rights side also. A theory of animal rights, as opposed to an argument for humanity in their treatment, looks flimsy. Wherever one starts in the vast moral-philosophical literature of humanrights theories it is difficult to see how they can be extended to the animal kingdom. Where do we begin and end? With higher mammals, fish, flies or fleas? Do amoebae have rights?

And just what are these rights to be? They can scarcely include the democratic right to equality under the law, or the social-democratic right to a decent standard of living. No one has yet suggested that animals should be entitled to welfare payments orthe vote, though in the Middle Ages there was a fashion for trying and hanging transgressive animals like dogs or pigs.

If animals have a basic "right" to be treated without cruelty, then that is saying no more than that people have a duty to treat them humanely (note the word), especially since no one has yet suggested that these rights should be reciprocal. To introducethe language of rights, as opposed to charity and pity, is, oddly enough, to make the same mistake of anthropomorphising non- human creatures.

"I know my cat has a soul," W H Auden said. But it was he, too, who envisaged with dejection the day when "justice is replaced by pity as the primary human value". There lies the distinction. Justice should be the primary value for dealings among human beings. Wherever we draw the line, however we decide we should treat animals, it can only be based on pity and compassion, not on the concept of rights.

There is a connection between the American "pro-life" activists who have taken to killing the staff at abortion clinics and the animal liberationists who, if unchecked, will soon do the same to scientists and farmers. In either case, the arguments must be made in logical and ethical terms. Righteousness does not justify anything.