Peter Singer, the groundbreaking ethicist whom The New Yorker calls the most influential philosopher alive teams up again with Jim Mason, his coauthor on the acclaimed Animal Factories, to set their critical sights on the food we buy and eat: where it comes from, how it is produced, and whether it was raised humanely.

The Ethics of What We Eat explores the impact our food choices have on humans, animals, and the environment. Recognizing that not all of us will become vegetarians, Singer and Mason offer ways to make healthful, humane food choices. As they point out: You can be...