According to the Dominant Western tradition, the natural world exists for the benefit of human beings.

It is easy for us to criticize the prejudices of our grandfathers, from which our fathers freed themselves. It is more difficult to distance ourselves from our own views, so that we can dispassionately search for prejudices among the beliefs and values we hold

In a situation where many national leaders do the same thing and look out for national interests, and with an issue like global warming, you're likely to get no solution, so I think you have to have some kind of ethical trump on some of those issues.

Can we really believe that we are living a good life, an ethically decent life if we don't do anything serious to help reduce poverty around the world and help save the lives of children or adults who are likely to die if we don't increase the amount of aid we are giving.

Suppose I grant that pigs and dogs are self-aware to some degree, and do have thoughts about things in the future. That would provide some reason for thinking it intrinsically wrong to kill them - not absolutely wrong, but perhaps quite a serious wrong. Still, there are other animals - chickens maybe, or fish - who can feel pain but don't have any self-awareness or capacity for thinking about the future. For those animals, you haven't given me any reason why painless killing would be wrong, if other animals take their place and lead an equally good life.

Surely there will be some nonhuman animals whose lives, by any standards, are more valuable than the lives of some humans.

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