Originally Posted by Boobzooka

Empathy is the answer. Sane people do not eat eachother unless they're literally starving, because most of us are capable of identifying with other human beings, at least on the most basic "I don't want to die" level. I extend that courtesy to other species as far as possible.

I have grown to appreciate that I am an animal too, made of the same stuff, evolved under the same conditions, with a similar set of practical emotions based on fulfilling physical and social needs. There's no supernatural line between us, just a lucky combo of slightly superior intelligence and opposable thumbs.

Of course all life isn't equal. A chicken is an infinitely more complex lifeform than a tomato. We all generally agree not to eat chimps and dolphins because we respect their intelligence. Then there are dogs, about as smart as a young human child, and more emotionally mature. Not far below dogs are pigs. Drawing a line there seems completely arbitrary. At what point does a sentient being become too dumb to respect their desire to live? I believe the wisest answer, under ideal conditions, is anything with a fully developed brain is probably self-aware enough that it would prefer not be eaten. That leaves plants, and some very basic shellfish, biologically incapable of individualism or having an opinion about what happens to them. Insects seem like a grey area I'm not going to lose sleep over; I don't worry when they hit my windshield, and protecting crops from them isn't a major moral dilemma for me, but if I see a spider inside I'll catch and release it outside instead of smashing it. Why not? Live and let live.

Now I'm not saying my life is of less value either. If I was lost in the jungle, Darwin's law is in effect. Vegetarianism is a moral luxury afforded by civilization. But when you have a choice, when it's not kill-or-die, then that decision carries a moral burden. As creatures capable of conscience, we can either embrace the nihilistic reality of a universe that doesn't seem to give a shit, or try to live as if life is a test and our decisions matter.