Well that is certainly an interesting argument, and something I've never considered before (which I find quite surprising, since I tend to 'be all over' this sort of thing). As for what is sentient, that is a tough question, is it the ability to recognise ones self (like the
mirror test, which all great apes pass, dolphins, orcas, elephants, and european magpies pass too)? Is it the ability to learn? Is it the ability to make language? Feel pain? It's a hard thing, because how are we to judge, maybe we are the ones who aren't understanding of the other animals, maybe we are missing something to make this judgement? I guess to me, all mammals are probably sentient, definitely all apes/monkeys, with reptiles/birds next in line for possibility, then fish, then amphibians, then insects... But I have no real backing for all that.
I mean, eating a vegetarian diet (which I don't just for the record), isn't the issue, it's more the fact of where and how we get our food from in the first place. If you look at somewhere like Obernewtyn, they grow all their own food (largely I think), and harvest it using humans and beasts, and it's all organic, which is what would clearly be the best thing (even if it might not be entirely feasible right now).
This does make me rethink a few things, that grains and vegetables might not be so 'green'. Though I'd say that buying locally from a farmer's market, and opting for organic produce is probably the closest we can get to an ethical, and environmental 'good' option.
