This sequel to In Defense of Animals, published twenty years ago, contains fourteen new essays, three revised essays and one that has been reprinted unchanged. Claiming that ‘philosophers served as midwives of the animal rights movement in the late 1970s’, Peter Singer devotes Part I to ‘The ideas’. The second edition displaces the now well-published philosophers found in the previous edition (e.g., Tom Regan, Stephen Clark, Mary Midgley) for a new generation of thinkers. They argue for ‘a new approach to the wrongness of killing, one that considers the individual characteristics of the being whose life is at stake, rather than that being’s species’. An arresting example is David DeGrazia’s suggestion that linguistically trained apes and dolphins are persons, while other members of their species are borderline persons. His justifications are that linguistically trained animals are exceptionally talented by comparison with their lower-IQ species confrères, and that learning a language means one is capable of more complex thought.