So far as this argument is concerned nonhuman animals and infants and retarded humans are in the same category; and if we use this argument to justify experiments on nonhuman animals we have to ask ourselves whether we are also prepared to allow experiments on human infants and retarded adults; and if we make a distinction between animals and these humans, on what basis can we do it, other than a bare-faced - and morally indefensible - preference for members of our own species?

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.

At present scientists do not look for alternatives simply because they do not care enough about the animals they are using.

The prescription of the equality of human beings is not a description of an alleged actual equality among humans: it is a prescription of how we should treat human beings.

To turn the other cheek is to teach would-be cheats that cheating pays.

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?

For most humans, especially for those in modern urban and suburban communities, the most direct form of contact with nonhuman animals is at meal time: we eat them.... The use and abuse of animals raised for food far exceeds, in sheer numbers of animals affected, any other kind of mistreatment.