Freddie at the group blog the League of Ordinary Gentleman probes the philosophical underpinnings of vegetarians/vegans and contends that they are insufficiently developed.
I think he’s wrong in suggesting that vegetarians haven’t devled deeply into these issues: there’s quite a vast philosophical literature on the subject that has sprung up in the last 30 years, and there are accounts of why animals matter morally that are as good as any other philosophical theory in ethics. (Which doesn’t mean they’re problem free, of course.) But more to the point, I don’t think you need a fully developed philosophical view to find vegetarianism compelling.
Almost everyone admits, in practice if not theory, that animals can suffer. And nearly everyone admits that it’s a moral truism that you shouldn’t cause unnecessary suffering. From those two simple, commonsense premises, it follows pretty quickly that you shouldn’t cause animals unnecessary suffering.
Throw in a few basic factual premises about the conditions under which animals are raised for food, and I think you arrive in short order at the minimal conclusion that our current system for raising animals for food (and probably most other feasible systems) is morally objectionable to say the least.
None of this requires you to make any major conceptual shifts in your worldview, such as accepting a particular theory of value or animal “rights” or whatnot, merely to draw a conclusion from premises that you (probably) already accept. It’s true that there are some people who claim to believe that animals don’t suffer, or that their suffering doesn’t matter. But the widespread revulsion at, say, the antics of Michael Vick indicate that this is a minority position.
In this sense, vegetarianism is like a lot of other reform movements: it doesn’t offer new values so much as try to make explicit the implications of values that people already accept. Why would you treat a pig in ways you would never dream of treating your dog or cat? The obstacles to reform are probably more institutional, psychological, social, and practical impediments than logical ones.
I’m, of course, all for investigating the question of whether animals have a right to life (as opposed to a right not to be made to suffer), but as far as the practical question goes, this makes almost no difference. Assuming there are idyllic farms where animals are allowed to roam freely and express their particular natures, do not have their tails docked or beaks clipped, are not castrated without anesthesia, and are killed suddenly and painlessly, these farms represent a tiny (if not nonexistent) percentage of meat production in industrial nations. For all practical purposes, avoiding the products of factory farms means being a near or total vegetarian.