If you put it as “complex nervous systems” it sounds pretty deflationary. What's so special about a complex nervous system? But of course, that complex nervous system allows you to do calculus. It allows you to do astrophysics… to write poetry... to fall in love. Put under that description, when asked “What’s so special about humans...?”, I’m at a loss to know how to answer that question. If you don’t see why we’d be special… because we can do poetry [and] think philosophical thoughts [and] we can think about the morality of our behavior, I’m not sure what kind of answer could possibly satisfy you at that point.
...I could pose the same kinds of questions of you... So God says, “You are guys are really, really special.” How does his saying it make us special? “But you see, he gave us a soul.” How does our having a soul make us special? Whatever answer you give, you could always say… “What’s so special about that?”
My view [is] that what morality boils down to is, “Don’t harm, and do help.” And now the question is, “Can creatures like chickens and cows be harmed?” And the answer is, “Of course they can.” Consequently, I think it’s immoral to harm them. And that seems to me to provide a very strong moral reason to be vegetarian, to not wear leather... it seems to me that our treatment of animals is morally appalling... and that we ought to radically revise the way we live, precisely because they feel pain, they can be hurt, and we’re constantly hurting these creatures!
A vegetarian in his everyday life, [Shelly Kagan] orders meatless meals when he flies. Airlines, however, sometimes fail to deliver on such requests. If that happens, and he is offered a meat meal that he knows will be thrown out if he doesn't eat it, he'll eat it. In these circumstances-in contrast to buying meat at the supermarket-his consumption of meat seems to make no difference to the demand for it.
Peter Singer and James Mason, The Ethics of What We Eat: Why Our Food Choices Matter (2007), p. 282