Contemporary animal rights and animal welfare advocates often make use of philosophers in the articulation and advancement of their movement. Sometimes a philosopher is merely trotted out for perfunctory abuse because of his animal-unfriendly philosophical views (that philosopher usually being the seventeenth-century philosopher René Descartes). This is not always altogether unfair, especially in Descartes’ case, as his view that animals are incapable of feeling pain strikes most today as patently absurd, and his indifferent depictions of experimentations upon still living animals strike most as horrifying.
The works of Immanuel Kant (an eighteenth-century philosopher) and John Stuart Mill (a nineteenth-century philosopher) have been used more substantively in animal advocacy movements, though. John Stuart Mill’s philosophy (utilitarianism) was actually already fairly animal-friendly. He believed that in any given situation the right action would be the action that tended to minimize the suffering and pain, and maximize the pleasure and happiness, of all interested parties. He further thought that the suffering, pain, pleasure and happiness of animals should be included in this calculus. Peter Singer’s Animal Liberation is a contemporary discussion of how such a utilitarian philosophy should impact our treatment of animals.
Another philosopher often discussed within animal advocacy movements is Immanuel Kant. Kant himself did not think that we had any direct ethical duties to animals. He believed that the only reason we should avoid being cruel to animals is that in doing so we might develop cruel habits that we would inflict on other people. According to Kant, we only owe ethical duties to rational beings, and animals are not included in that group. Still, animal rights advocates have been attracted to Kant’s philosophy for many reasons. One reason is that in Kant’s philosophy each individual to whom we do owe direct ethical duties can never be sacrificed to the happiness of others, no matter how much happiness might result. Kant posited that rational beings have inviolable rights, owed to them because of their rational nature, and that each must be treated as an end in herself. So, while in utilitarianism the right thing to do, that action which maximizes happiness, might involve inflicting pain on someone, in Kant’s philosophy that would never be acceptable. Animal rights advocates often argue that animals too have these sort of rights, and that they should never be sacrificed under the auspices of the greater good, either as food or as the subjects of medical experimentation.
For more on this topic see the Overview or Detailed Discussion.