[nudist]

It's not a scientific judgement? How can you say it's OK to kill plants but not "animals," considering they are made of essentially the same thing? Where is the line?

It's fairly easy to trace the evolution of the nervous system from simple single-celled organisms to modern animals. Moral repugnance is a purely human invention.

[hyperbovine]

Plants and animals are made of essentially the same thing? Plants have no nervous system and absolutely no capacity for suffering. It is impossible to inflict pain on a plant. By contrast, most animals are capable of experiencing physical and even mental anguish. Once you admit this, good luck trying to build a coherent moral argument for why human suffering should be abhorrent while all other forms of animal suffering are fair game. This is "speciesism," a term introduced by the philosopher Peter Singer in his famous book Animal Liberation. I have never read a convincing refutation of the argument therein.

There is a line. It simply requires some thought to elucidate it.

[nudist]

Pain?

When you poke a Euglena[1] with a pin while looking at it under a microscope, its sensors detect an intrusion and immediately start flapping the flagella (the thing it uses for locomotion, analogous to a leg) to get out of the way. That's a super-simple nervous system. Many plants do this as well, using a slow production of chemicals which move branches and leaves.

As you get more advanced, going up the biological totem pole, every creature uses that exact same sensor => action mechanism. Pain is the brain's complex interpretation of the pin prick, and an animal attempting to remove itself from the source of the pain is the same as activating the flagella.

My brain has mirror neurons which make me literally feel your suffering as you experience it, which is why humans are so against "pain" and "suffering". It's also why I personally will never injure another human, or even another animal, purposefully.

Is it more "wrong" in any scientific way to injure a human instead of a dolphin or a bear or a chimp or a plant -- or even to break a window? Absolutely not. This is why science should never be used to prove or disprove human "morals" and morals should never dictate the functions of science.

[1] http://en.wikipedia.org/wiki/Euglena

[hyperbovine]

I admit that I had never heard of the Euglena before, although the same article seems to be suggesting that the very characteristics you have pointed out cause some scientists to want to classify it as an animal. The suggestion being that the hallmark of "animality" is the ability to feel things.

In any case, I do not (intentionally) consume a great deal of Euglena, so I will content myself with pointing out that grains, vegetables, and fruit upon which I rely to replace the inhumane bounty of factory farming never bled, farted or blinked, and never will. I'm not trying to sound like a holier-than-thou vegetarian here; I'm not, and I have always made a point of not judging how others approach this issue. But if you're going to deconstruct my reasoning, the use of a red herring is discouraged.

As to your last question, the answer is "yes", and the case has been made in the book I mentioned far better than I can here. If you equate breaking a window with killing a dolphin, bear, or chimp, well, that speaks volumes.

[anigbrowl]

I'll cheerfully refute it: lower animals do have the capacity to feel pain (so we shouldn't be cruel) but not, it appears, the capacity to hypothesize about the future - that is, pigs don't suffer anxiety over the probability of ending up getting slaughtered for bacon when they're sufficiently bulky.

this is a major qualitative difference between us and other animals (that we know about).

[brl]

Since we really have no way to know for sure how much thinking about the future a pig does while confined on a grim industrial farm or exactly how much anxiety that pig experiences nervously worrying about the future, maybe we could give them the benefit of the doubt?

[hyperbovine]

Well, if you concede the cruelty point, then you are pretty much in agreement with the animal liberation school; I'm unclear what's being refuted. The point is not that eating other animals is wrong--some believe so (not me), but it's a tough argument to swallow. Only that we have no right to make them suffer.

I think people often confuse the two because if you buy into the animal liberation argument, then the first thing to go is all the beef, pork, poultry, eggs and dairy that come from factory farming, i.e. everything. So functionally you wind up vegetarian, if not vegan. Now that we're seeing more places like Polyface Farms, Neeman Ranch, etc. open up, hopefully that situation will change in the future.