It is absurd to assign rights to animals, argues Roger Scruton in response to the 'moral humbug' of his critics. Recent correspondence prompts me to add to the argument of my article about why the concept of animal "rights" is "wrong" (É«ºÐÖ±²¥S, June 28).

The concept of a right makes sense only when applied to the members of a moral community - a community whose members have sovereignty over their individual lives and who settle their disputes by negotiation. The concept of a right takes its meaning from this context, as do the concepts of duty and responsibility. To attribute rights to a creature, therefore, is to view it as a member of the moral community - as the kind of thing that has, or can have, duties or responsibilities too.

Those who defend animal rights seldom ask themselves what the concept of a right is for. If rights are just interests, then of course animals have them. But that misses the feature that endows rights with their moral importance. Rights express the sovereignty of the individual; they cannot be overridden, only relinquished. Your right to life, therefore, prohibits me from killing you. A mere interest can be overridden, when greater interests prevail. That is why it is important to know whether animals have rights. If they do have rights, then we cannot kill them - and every twist of the fork in the garden becomes a crime. Extreme animalists and pacific vegetarians may take this line, and I am bound to respect them. But I refuse to respect the moral humbug of those who invent rights for the animals that appeal to them, and then arbitrarily choose to ignore those rights when the desire for a slice of ham or the thought of a few hours fishing tempt them in another direction.

But, of course, if you see rights as I have suggested, it becomes absurd to act as though animals had them. For you would then be forced to treat animals as members of the moral community, with the responsibilities and duties that stem from that. You would be forced to take towards them attitudes - such as accusation, punishment, judicial prosecution - which are the price exacted for the gift of sovereignty. Richard Ryder responds to this by saying that you must in that case deny rights to infants and imbeciles, since they cannot take up the burden of duties and responsibilities. I argue that infants and imbeciles belong to the same kind as you and me: the kind that grows into a fully fledged member of the moral community. It is this that causes us to extend to them the shield we consciously extend to each other and that is built collectively through our moral dialogue.

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It is not just that dogs and bears do not belong to the moral community. They have no potential for membership: they are not the kind of thing that can settle disputes by dialogue, that can exert sovereignty over its life and respect the sovereignty of others, that can respond to the call of duty or take responsibility in a matter of trust.

It should be noted, also, that we do not accord to infants and imbeciles the same rights as we accord to normal adults. Their disabilities have moral consequences. And although infants cause us no difficulties, imbeciles cause us real moral problems. These problems confirm what I say about the concept of a right, rather than refute it.

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Mr Harwood, from the philosophy department at Reading, accuses me of arguing that cruelty to animals is justified if it is part of ritual slaughter. (É«ºÐÖ±²¥S Letters, August 9). But there are two rival notions of cruelty at work in current debates. One describes an act as cruel if it "causes unnecessary suffering". This is the normal legal conception, and I should like to question it. For what exactly do we mean by necessary? The suffering involved in ritual slaughter is necessary - necessary to ritual slaughter - even if it is more than is necessary to cause the animal's death. This definition, therefore, is compatible with anything we should choose to do, provided we can make some independent case for doing it.

I prefer to define cruelty intentionally. An act is cruel if it involves the deliberate infliction of suffering for its own sake, and with a view to relishing it. Bear-baiting comes into this category; but angling and hunting emphatically do not. Kind people inflict massive suffering on animals - as gardeners and vets habitually do. But only cruel people can take delight in this suffering, and want it, not as a means, but as an end in itself. Once again, we must remember that the sources of morality are many, and that the distinction between vice and virtue will not be delivered by a moral philosophy that remains fixated, to the exclusion of all other considerations, on the concept of a right.

Roger Scruton is visiting professor of philosophy at Birkbeck College.