In Ted Honderich (ed.), The Oxford Companion to Philosophy, Oxford, 1995, p. 897
The view that we should avoid eating meat or fish has ancient philosophical roots. In the Hindu Upanishads (about 1000 BC) the doctrine of reincarnation leads to opposition to eating meat. Buddha taught compassion for all sentient creatures. Buddhist monks were not to kill animals, nor to eat meat, unless they knew that the animal had not been killed for their sake. Jains hold to ahimsa, or non-violence toward any living creature, and accordingly do not eat meat.
In the Western tradition, Genesis suggests that the first diet of human beings was vegetarian, and permission to eat meat was given only after the Flood. After that, vegetarianism gains little support from either the Jewish or Christian scriptures, or from Islam. Philosophical vegetarianism was stronger in ancient Greece and Rome: it was supported by Pythagoras, Empedocles, Plutarch, Plotinus, Porphyry, and, in some passages, Plato. Pythagoreans abstained from eating animals partly because of their belief that humans and animals share a common soul, and partly because they appear to have considered the diet a healthier one. Plato shared both these views to some extent. Plutarch's essay On Eating Flesh, written in the late first or early second century of the Christian era, is a detailed argument for vegetarianism on grounds of justice and humane treatment of animals.
Interest in vegetarianism revived in the nineteenth century, on grounds of health and humanity towards animals. Notable vegetarian thinkers included the poet Percy Bysshe Shelley, Henry Salt (who wrote a pioneering volume entitled Animals' Rights), and George Bernard Shaw, who said that he put into his plays the ideas that he learned from Salt. In Germany Arthur Schopenhauer urged that ethically we should become vegetarian, were it not for the fact that the human race cannot exist without animal food 'in the north'!
Since the 1970s vegetarianism has gained strength from three major lines of argument: health, ecology, and concern for animals. The first of these grounds rests on a scientific, rather than philosophical, claim and will not be discussed further here. Ecological concerns about eating meat arise from the well-documented inefficiency of much animal-raising. This applies especially to intensive farming, in which grain is grown on good agricultural land and fed to animals confined indoors, or in the case of cattle, in crowded feed-lots. Much of the nutritional value of the grain is lost in the process, and this form of animal production is also energy-intensive. Hence concern for world hunger, for the land, and for energy conservation provide an ethical basis for a vegetarian diet, or at least one in which meat consumption is minimized.
Arguments for a reassessment of the moral status of animals have also given support to vegetarianism. If animals have rights, or are entitled to have their interests given equal consideration with the similar interests of human beings, it is easy to see that there are difficulties in claiming that we are entitled to eat non-human animals (but not, presumably, human beings, even if through some accident they are at a similar mental level to the animals we do eat). These ethical arguments for vegetarianism may be based on the view that we violate the rights of animals when we kill them for our food, or on the more utilitarian grounds that, in raising them for our food, we cause them more suffering than we gain by eating their flesh.
Keith Akers, A Vegetarian Sourcebook, 2nd edn. (Denver, 1989).
Francis Moore Lappé, Diet for a Small Planet, 2nd edn. (New York, 1985).
Tom Regan and Peter Singer (eds.), Animal Rights and Human Obligations, 2nd edn. (Englewood Cliffs, NJ, 1989).