My first extended work of philosophy was a study of Aristotle's ethics in the light of his biology (Aristotle's Man). My second was an impassioned work on the moral status of non-human animals (The Moral Status of Animals), and my third, a more decorous study of non-human experience and motivation, in the light of current biological theory and ethological reports (The Nature of the Beast). Later books were directed rather at cosmological and epistemological aspects of the philosophy of religion, though almost all of them also made some glancing reference to our biological nature, and to the treatment of non-human animals and our ‘environment’ (see especially How to Think about the Earth). Various essays on non-human animals have been collected in Animals and their Moral Standing, and on the political life of the human animal in The Political Animal.