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.

Dolphins are social mammals, capable of enjoying their lives. They form close bonds with other members of their group.

Each of us spends money on things that we do not really need. You could take the money you're spending on those unnecessary things and give it to this organization the Against Malaria Foundation which would take the money you had given and use it to buy nets to protect children. And we know reliably that if we provide nets, they're used, and they reduce the number of children dying from malaria. Fortunately more and more people are understanding this idea, and the result is a growing movement effective altruism.

The future of the world depends on how well we meet it.

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.

If we compare a severely defective human infant with a nonhuman animal, a dog or a pig, for example, we will often find the nonhuman to have superior capacities, both actual and potential, for rationality, self-consciousness, communication and anything else that can plausibly be considered morally significant.

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.