Instead of defending one particular ethical theory in order to ground a concern for nonhuman animals, some animal ethicists appeal to “common sense” moral principles when promoting an animal liberation ethic. Their assumption is that they can just as well use the beliefs that (most) moral agents already endorse in order to encourage them to take the interests of nonhuman animals seriously. Perhaps, the assumption is that it is not necessary to employ a confusing, complex, philosophical theory in order to illustrate that moral agents are morally obligated to grant basic moral consideration to nonhuman animals.
Steve Sapontzis: begins with the principles of “every day morality” (reducing suffering, developing moral virtues, fairness) and aims to demonstrate that moral consistency requires us to extend whatever moral protection is offered to human beings to nonhuman animals (typically, this moral protection comes in the form of “rights”). He rejects the view that we can exploit or discount nonhuman animals because they are not rational, Rationality is not the criterion of moral considerability; having interests is what entitles a being to moral consideration. Sapontzis goes on to argue that non-human animals have interests and the existence of interests justifies including them in the moral community. A central component of Sapontzis’ thought is one of fairness, which requires that we extend the same moral protection to nonhuman animals that we grant to human beings. He is best known for his book Morals, Reason, and Animals. You can read a chapter from his book here.
Mylan Engel draws on the moral beliefs that individuals already endorse in order to illustrate that they should be both vegan and opposed to animal research. He rests his case on beliefs that individuals already hold in order to block spurious objections to mainstream ethical theories, like utilitarianism and deontology, while “providing an argument for the immorality of eating meat which does not rest on any particular ethical approach (857).” Such beliefs include (but are not limited to) the following: Other things being equal, a world with less pain and suffering is better than a world with more pain and suffering, a world with less unnecessary suffering is better than a world with more unnecessary suffering, unnecessary cruelty is wrong and prima facie should not be supported or encouraged, we ought to take steps to make the world a better place. Since both the consumption of animal flesh and the use of animals for biomedical research violate our basic moral beliefs, we should oppose both biomedical research and animal agriculture. Click here to read his article “The Immorality of Eating Meat.”