What place should non-human animals have in an acceptable moral system? These animals exist on the borderline of our moral concepts; the result is that we sometimes find ourselves according them a strong moral status, while at other times denying them any kind of moral status at all. For example, public outrage is strong when knowledge of “puppy mills” is made available; the thought here is that dogs deserve much more consideration than the operators of such places give them. However, when it is pointed out that the conditions in a factory farm are as bad as, if not much worse than, the conditions in a puppy mill, the usual response is that those affected are “just animals” after all, and do not merit our concern. Philosophical thinking on the moral standing of animals is diverse and can be generally grouped into three general categories: Indirect theories, direct but unequal theories, and moral equality theories.
Indirect theories deny animals moral status or equal consideration with humans due to a lack of consciousness, reason, or autonomy. Ultimately denying moral status to animals, these theories may still require not harming animals, but only because doing so causes harm to a human being’s morality. Arguments in this category have been formulated by philosophers such as Immanuel Kant, René Descartes, Thomas Aquinas, Peter Carruthers, and various religious theories.
Direct but unequal theories accord some moral consideration to animals, but deny them a fuller moral status due to their inability to respect another agent’s
rights or display moral reciprocity within a community of equal agents. Arguments in this category consider the sentience of the animal as sufficient reason not to cause direct harm to animals. However, where the interests of animals and humans conflict, the special properties of being human such as rationality, autonomy, and self-consciousness accord higher consideration to the interests of human beings.
Moral equality theories extend equal consideration and moral status to animals by refuting the supposed moral relevance of the aforementioned special properties of human beings. Arguing by analogy, moral equality theories often extend the concept of rights to animals on the grounds that they have similar physiological and mental capacities as infants or disabled human beings. Arguments in this category have been formulated by philosophers such as Peter Singer and Tom Regan.