When children see animals in a circus, they learn that animals exist for our amusement. Quite apart from the cruelty involved in training and confining these animals, the whole idea that we should enjoy the humiliating spectacle of an elephant or lion made to perform circus tricks shows a lack of respect for the animals as individuals.

My work is based on the assumption that clarity and consistency in our moral thinking is likely, in the long run, to lead us to hold better views on ethical issues.

Interest in business ethics courses has surged, and student activities at leading business schools are more focused than ever before on making business serve long-term social values.

I don't understand the notion that modern farming is anything do to with nature. It's a pretty gross interference with nature. I think it ought to be governed by the standards of how it affects the individual animals, just as we'd want to deal with institutions that deal with humans by how they affect individual humans.

My fear is that that's what's going to happen with robotics and the military. Importantly, this discussion has to involve not just the scientists, but also the political scientists. It's got to be a multidisciplinary discussion. You can't have it be another repeat of what happened with the people working on the atomic bomb.

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

Somebody who eats twice as much factory-farmed products as he or she needs to is clearly doing twice as much damage to the planet. From a utilitarian point of view, that's twice as bad.