Did Steve Irwin get what he had coming? LAURENCE FITZPATRICK, Manchester
I never watched his show, so I'd better leave this one to those who have.
What do you think of the people who are trying to shut down Huntington Life Sciences laboratories? DON ROYAL, Kent
I'd like to see HLS shut down, because there has been appalling animal suffering there. But the problem isn't just HLS, it's the attitude we have to animals. Factory farming is a much bigger problem - the number of animals suffering there is vastly greater, and everyone who buys factory farm products is responsible for the continuation of that cruelty. So to change that we need to persuade the general public to change their attitude to animals. On that, the tactics used against HLS don't help. They make the animal movement seem like fanatics, or even worse, terrorists. Our case for animals rests on ethical foundations. When we descend to abuse and harassment, people lose sight of that.
Where should one draw the line between legitimate and illegitimate direct action? ALASTAIR BANTON, London
I support civil disobedience, in the tradition of Gandhi and Martin Luther King. I also support animal activists who trespass to document animal abuse and rescue animals who are suffering or dying. I do not support the use of violence or intimidation.
Isn't it contradictory to ascribe human-based rights to animals? Surely it is absurd to apply a purely human concept to an animal who has no hope of ever understanding such a thing? ZAKI NAHABOO, London
Not at all. Anyone who ascribes rights to babies or humans with intellectual disabilities must be willing to attribute rights to beings who can't understand the concept. It's the moral agents, the ones who are acting, who need to understand the concept. Those to whom we attribute rights, do not need to understand these concepts.
Why should we assign rights to animals when we already recognise duties (of care, preservation of their species, etc) towards them? If animals have a right to life, for example, must we protect them against natural predators in the wild? FRANCO FUBINI, Cambridge
Unfortunately, we don't come anywhere near fulfilling the duties we have to animals. If we did, we wouldn't be bringing misery to the lives of millions of factory farmed animals, for no reason except that we prefer the taste of their flesh to other, cruelty-free and sustainable ways of feeding ourselves. As for protecting prey from predators, if we did that we would be upsetting the ecological system, and the prey would soon become too numerous and starve.
Should we force dogs and lions to stop eating meat? MICHAEL GAYLARD, Bangkok, Thailand
Dogs who live with us, we don't need to feed meat, and they can do fine without it. Lions, no - I've already answered this.
You have argued we should not eat other animals but you draw a line at the oyster. How do you know oysters aren't sentient? NIC RILEY, London
They don't have a brain orcentral nervous system, so it is hard to imagine that they can feel pain. But if you have doubts about it, don't eat them.
Do you have any pets? MATTHEW BROWN, New York
Would turning to a vegan/vegetarian diet be a first step towards restoring our moral well-being? NITIN MEHTA, Croydon
I'm more interested in the consequences of that change than in our moral well-being. Going veggie is a very important step, both for what it does for the animals, and what it does to reduce pressure on the environment. It has also been shown to be the single most effective thing that the average person can do to reduce greenhouse gas emissions.
I would like to be a vegetarian but I hate nuts, tofu and vegetables. Any tips? CARL REID, Edgware
Tofu and nuts are good sources of protein, but assuming you're an adult - and from your name, I'd guess you are not pregnant or breast-feeding - you don't need to worry too much about protein. You'll get enough if you eat bread, rice, potatoes and pasta. Eat lots of fruit for fibre and vitamins. For the same reason, go for wholemeal bread and pasta where you can, and brown rice.
If you were starving and meat was the only sustenance available, would you eat it? LILY WILSON, Wexford, Ireland
Yes. Everything depends on the consequences. Eating meat because you like the way it tastes is totally different from eating it to survive.
What's the most effective retort I can use when criticised for being a vegetarian? DAVID BRADFORD, Surrey
Try asking them why they are not vegetarian.
You have said that if you had to decide between shooting 10 healthy cows and one healthy human you would have a difficult choice, Why? FLORA HAMILTON, Edinburgh
I never said that. On the contrary, I've written that it is much worse to kill a being who is aware of having a past and a future, and who plans for the future. Normal humans have such plans, but I don't think cows do. And normal humans have family and friends who will grieve their death in ways more vivid and longer-lasting than the way cows may care about other cows. (Although a cow certainly misses her calf for a long time, if the calf is taken from her. That's why there is a major ethical problem with dairy products.) If I really had to make such a decision, I'd kill the cows.
In many parts of the world dogs roam free and are sterilised by animal welfare groups. Would it be less cruel to euthanise them? And are dogs confined in homes - often alone all day - any better off than dogs taking their chances on the streets? CINDY MILBURN
Dogs are pack animals, and shouldn't be left alone all day. I'm not opposed to euthanasia in some circumstances, but if the dogs are doing all right on their own, it's better to sterilise them and set them free again.
Are zoos immoral? JANISE SCHULER, Greenwich
Most of them are, because they confine animals for our amusement in ways that are contrary to the interests of the animals. But if zoos really put the interests of the animals first, and only then find ways for us to observe them, they are not immoral.
Did caring for your mother as she developed Alzheimer's change your views about the propriety of terminating the lives of young children with severe mental retardation? LEILA MORRISON, Bath
Would you kill a disabled baby? KAREN MEADE, Dublin
Yes, if that was in the best interests of the baby and of the family as a whole. Many people find this shocking, yet they support a woman's right to have an abortion. One point on which I agree with opponents of abortion is that, from the point of view of ethics rather than the law, there is no sharp distinction between the foetus and the newborn baby.
How does it feel to be compared to a Nazi given your grandparents died in the Holocaust? ELLA LJUNGGREN, London
It's offensive and frustrating. It's sad that people have so little understanding of either my views, or what the Nazis really believed.
Do you advise people to give a fifth of their income to charity? DEBRA FREEMAN, Perth
I give more than a fifth, nowadays, but I usually suggest that people give 10 per cent. Of course, it all depends on people's circumstances, but when there are so many people dying from poverty-related causes giving a tenth of our income to organisations such as Oxfam or Unicef seems a for moral decency.
I am in debt (to financial institutions). Should I prolong my debt repayments by contributing towards alleviating poverty, or should I make my repayments and then give to charity? MARK MORGAN, Bath
Maybe you should cut your spending?
Does free will exist and if so, is it restricted to human beings, or can other animals have it? E CASTLE, Brighton
In a deep metaphysical sense, I don't think free will exists. But we, and some animals, can make choices, and that's real enough, whatever the causes of our choices.
What is the most immoral thing you have ever done? JAMIE BAXTER, Liverpool
Spending too much money on myself when others need it a lot more.
Is it impossible for the human race to reach its potential? PETER BRAHAM, West Yorkshire
Whatever it's potential, it's possible. But don't ask me if it will actually happen.
Would you say your fundamental ethical principle is that we should attempt to do least harm; and if so, the main problem this raises is knowing how to compare different kinds of harm? STEPHEN MORLEY
No, I think we should try to reduce harm as much as possible, which is different from ourselves doing the least harm. It isn't easy to compare different types of harm, but we have to do our best.
Are there moral absolutes, if so, what are they and why? RENAE MANN
The only moral absolute is that we should do what will have the best consequences for all those affected by our actions.
Your philosophy seems very heavy. What do you do to chill out? V J SINGH, London
Go hiking and get away from the crowds.
Is your species a plague on the planet? DAVID UNDERHILL, Alabama
We've certainly done a lot of damage to other species, but "plague" isn't the right term.
How do we deal with people like George Bush, who care nothing for truth or logic in their bid to get their own way? JULIA ISKANDAR, London
Try to get others to see them this way, so that they'll be voted out of office.
Thanks largely to your work, utilitarianism is now best known as " the baby-killing philosophy". Are you really maximising good consequences with this focus on infanticide? RICHARD PENNY Helsinki
I haven't focused on infanticide. It's always been a minor aspect of my work. The focus is that of my opponents, and the media.
Animal rights activists are often seen as dirty. How often do you wash? J MANN, by email
Once a month, whether I need it or not.
You once included Pride and Prejudice in a list of your top ten books. Was Jane Austen a feminist? CARRIE HOWARD, Manchester
Of course! Do you think Elizabeth Bennet meekly did whatever men told her to do?
Why should I be moral? KATIE FARRELL, New York
Well ... I've written a whole book on that topic How Are We to Live?, but in a single sentence: you'll find it more fulfilling, in the long run, to contribute to making the world a better place, than to think just of your own interests.
Do you ever live up to your surname and sing? WILSON EVANS by email
Yes, but if my ancestors were really singers, I'd like to know what happened to the staying-in-tune genes.