The ethical issues associated with non-human beings are related to the boundary of the moral community. In this regard vegetarianism concerns non-human beings. Reasons and purposes to be a vegetarian are based on the being to be considered, in other words, on the boundary of the moral community.
Generally we classify vegetarians according to kinds of food to be allowed. This is not only vague but also difficult to grasp the intent and purpose of vegetarianism. It is more important to classify it by the intent and purpose of vegetarians than by kinds of food that should be allowed. Therefore, it is worthwhile to categorize vegetarianism as vegetarians 'for human', 'for animals', 'for all life' and 'for environment'.
However, it seems not easy for each type of the vegetarians to justify itself. Arguments of vegetarianism based on human health and economic efficiency rather permit some restricted form of meat-eating. The vegetarianism for animals would be allowed to eat the animals raised for food without causing them unnecessary suffering. Vegetarianism for all living things brings about the same results. Vegetarianism for the environment and the ecosystem has to permit the meat-eating under the limits with no harm to the environment and the ecosystem.
From the arguments based on our health and economic efficiency, the suffering and the right of animals, and the conservation of the environment and the ecosystem, it does not follow that we are all to be vegetarian and we should not eat all meats. These arguments clearly show that excessive meat-eating is morally wrong, and indicate that demi-vegetarianism is more desirable than veganism.