“Suffering, by its nature, is awful, and so one needs an excellent reason to cause it. Occasionally, one will have such a reason. Surgery may cause a human being severe postoperatory pain, but the surgeon may be right to operate if that’s the only way to save the patient. And what if the sufferer is not a human, but an animal? This doesn’t matter. The underlying principle is that suffering is bad because of what it’s like for the sufferer. Whether the sufferer is a person or a pig or a chicken is irrelevant, just as it’s irrelevant whether the sufferer is white or black or brown. The question is merely how awful the suffering is to the individual.”

— Stuart Rachels, Vegetarianism (The Oxford Handbook of Animal Ethics, 2012, pp. 883-884)