"Animal liberation is also human liberation. Animal liberationists care about the quality of life for all. We recognize our kinship with all feeling beings. We identify with the powerless and the vulnerable, the victims, all those dominated, oppressed and exploited. And it is the non-human animals whose suffering is the most intense, widespread, expanding, systematic and socially sanctioned of all."

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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?

— Peter Singer