Human rights or dolphins' rights? You can't espouse all of the causes all of the time, says Aminatta Forna; TESTIMONY
it's Friday evening. A group of urban thirty- somethings is dining together. One woman asks whether the tuna in the pasta sauce was line- caught or not; she is extremely concerned and wants to be sure of the facts before she eats it. Dolphins get caught in tuna nets, she explains. Most of us know this and we consider the implications of eating tuna with appropriate gravity.

I've no intention of not eating my plate of food whatever the answer, but I'm shy of saying so. The man next to me isn't. He pipes up with some crack, broadly at the expense of dolphins and the dolphin-lover. Well! It was a rash action which, with hindsight, made a lager lout taking on the bulls of Pamplona appear over-cautious. The ensuing row went on almost until the end of the meal.

It's possible the woman knew he was a lawyer when she called him cynical and selfish. When she said it was people like her who made a difference to the world, I don't suppose she could have known that this unrepentant meat-eater dedicated his own time to fighting human-rights abuses in Turkey. That he was about to publish a book on the subject. That although he didn't appear to care about dolphins, he certainly cared about people.

Or perhaps she knew and just didn't care. This is the modern battle of ideas. A battle in which conversation has become a minefield. The multiplicity of causes, issues and campaigns today means that everyone feels strongly about something. From dolphins to domestic abuse, from elephant poaching to East Timor, there is something for everyone. The late 20th-century spawning of crusades is an effect of the documented shift of political activity and interest away from party politics towards individual issues. The trouble is that there are so many to choose from - and we don't all feel strongly about the same things.

"Compassion fatigue" was a phrase coined a few years back. Back then we'd done Band Aid and Live Aid; we'd Run the World; protested over treatment of the Kurds - twice; worn Red Noses every year, tackled another famine/oil- spill/ethnic-cleansing campaign; then ... enough!

Caring equally about all the causes with equal merits is worthy but impossible. But it wasn't compassion fatigue: people didn't stop caring, they just cared more selectively. In the Nineties most of us are likely to choose our charities and our causes, fighting only for those we feel most strongly about.

Today there are nearly 5,000 registered charities and new ones being registered at the rate of nearly two per working hour. A few years ago I made my choice and I've stuck to it. Third World causes are high on my list, as are human-rights abuses, torture victims and issues relating to gender- and race-equality. They are my priorities and I can get very het up over them indeed. Children and cancer research I know attract a lot of concern and so I reckon someone else is taking care of those. Veal calves and donkey sanctuaries? Well, I wish all animals could live a life of liberty and dignity but I'm afraid I'm not going to go out and demonstrate for it. Boarding-school survivors and Lloyds names - forget it.

Now, in theory it should be possible for every cause to have its followers, and that in itself would ensure that most of the world's concerns were being taken care of. Unfortunately it isn't so - because it is the nature of crusades to convert. And that's where vegetarians at loggerheads with human-rights activists come in. Like old-fashioned crusaders, the sword of self-righteousness in our hand, we battle for the souls of dinner-party guests and the moral higher ground.

People who care about animals think they are the rightful occupiers of the moral high ground. That's because they are the guardians of creatures who are small, often fluffy, and unable to safeguard their own rights. Human-rights activists believe people matter more than animals but that cuts no ice with animal-lovers. (Note: neither of them, it seems, care about tuna).

Political reformists consider themselves to be looking at the bigger picture and everyone else to be merely tinkering. Environmentalists give themselves pole position because they are saving the world and, without them, all is lost. And New Age spiritualists think it's all lost anyway and they're saving our souls for the great hunting ground in the sky. Put them together, add a few drinks too many and a long evening, and you have the ingredients for combustion.

In an American TV film He Said/She Said, screened recently, a woman explains why her sister didn't turn up to meet her fiance. "With your views on abortion," she explained, "she didn't think it would be right to sit at the same table as you."

Don't laugh. For me, it's Alan Clark. And if he knew me I believe he would agree we should never socialise together. He cares little for issues of gender- or racial- equality ... but is a committed vegetarian. I eat veal.

"Never discuss religion or politics," used to be the golden rule of civilised conversation. I propose a change to reflect the times. Never discuss religion, politics, vivisection, PC, cycling lanes, China, date rape, gender roles, positive discrimination, consumer power, nuclear power, black power, travellers' rights....