The essay argues that the moral principle underlying human rights should be extended to nonhuman animals and marshals philosophical and historical arguments for that extension. It surveys the treatment of domestic and wild animals and critically examines practices such as slaughter for food, recreational sport, commercial capture and exhibition, the use of birds and furs in fashion, and vivisection. The author reviews contemporary social and legal developments, highlights growing humane responses including dietary change, and assesses practical avenues for reform. The work concludes with concrete proposals for legal and social change and includes appendices and a bibliography.