‘Animal Liberation’ started a worldwide movement when it revealed the abuse of animals in factory farms and laboratories. It demonstrated that these and other practices were the cause of appalling and unnecessary suffering and therefore morally indefensible. In the fifty years since, science has further vindicated Peter Singer’s arguments about animal sentience, vegetarianism has become widespread, and the book has helped change the minds of millions. But the situation for animals has in many ways grown worse. Despite improvements in animal welfare in some regions – brought about in large part by this book – in many others the scale of their abuse has reached staggering new depths. This revised edition, of which about two-thirds is entirely new, documents these and other developments, such as the impact of meat consumption on climate and the spread of dangerous new viruses.