This paper argues that beliefs about human nature are central for animal ethics as beliefs about animal nature ground human treatment of animals. It shows that what constitutes animal nature is a contested question, and that animals have long been considered inferior to humans in Western thought. In Judaeo-Christian ethics, God gave humans dominion over animals. This exacerbated the long-established prejudice in Western culture in favour of rationality as the defining characteristic of human beings. Rene Descartes was influential in arguing that animals were but machines that moved and made sounds but had no feelings. In such a context it was easy to portray animals as quasi-clockwork animated robots — ‘furry clocks’. Jeremy Bentham first advocated the direct inclusion of animals in our ethical thinking, introducing the concept of sentience, or the capacity to feel pleasure and pain, as the central criterion. Peter Singer's work is in this tradition. He also popularised the notion of speciesism — a bias in favour of one's own species. Now, Martha Nussbaum has introduced a new approach, the capabilities approach, a Quality of Life approach which lists ten capabilities, nine of which apply to animals as part of their nature. It applies to the whole range of animals (and throughout this paper the term ‘animals’ refers to sentient animals unless otherwise specified) — companion animals, farm production animals, animals in zoos, rodeos, museums and laboratories. Her work is the main focus of this paper. It is argued, therefore, that the capabilities approach contributes to understanding the relation of notions of animal nature to animal welfare, and what a good life for animals entails.