If you go back in time you'll find tribes that were essentially only concerned with their own tribal members. If you were a member of another tribe, you could be killed with impunity.

That's a central part of philosophy, of ethics. What do I owe to strangers? What do I owe to my family? What is it to live a good life? Those are questions which we face as individuals.

I believe that in this new world that we live in, we often have a responsibility, you know, to actually go beyond the thou shalt nots - that is, the not harming others - and say we can help others and we should be helping others.

If penicillin had been judged by its toxicity to guinea pigs, it might never have been used by man.

No consideration at all is given to the interests of the "pests" - the very word "pest" seems to exclude any concern for the animals themselves. But the classification "pest" is our own, and a rabbit that is a pest is as capable of suffering, and as deserving of consideration, as a white rabbit who is a beloved companion animal.

When fish experience something that would cause other animals physical pain, they behave in ways suggestive of pain, and the change in behaviour may last several hours.

The statement "I am in pain" may be one piece of evidence for the conclusion that the speaker is in pain, but it is not the only possible evidence, and since people sometimes tell lies, not even the best possible evidence. Even if there were stronger grounds for refusing to attribute pain to those who do not have language, the consequences of this refusal might lead us to reject the conclusion. Human infants and young children are unable to use language. Are we to deny that a year-old child can suffer?