In writing what has become known as “the bible of the animal-liberation movement,” ethicist Peter Singer did not set out to make us love animals any more than we may (or may not) already have. Instead, he set out to persuade us on rational grounds that humans (themselves animals) must reject causing unnecessary pain to other beings who can “suffer and/or experience enjoyment.” How can it be moral to torture pigs — for torture it is, as Singer matter-of-factly puts forth the realities of farming — just so we can have pork for dinner? “Speciesists,” Singer argues, drawing a comparison with racists and sexists, “allow the interests of their own species to override the greater interests of members of other species.” Singer, who published Animal Liberation in 1975, remains an influential, if controversial, voice to this day.