Well, the utilitarianism has also stuck with me, and I lean that way on a lot of philosophical/ethical questions. I didn't really realize it until a few years ago while dating someone relatively well-known in utilitarian/rationality circles and had some eye-opening conversations with her and her friends about rights and the like (lots of things I'd never really thought through to their logical conclusions led to a softening of my stance on some stuff).

I spent a lot of years being a natural rights libertarian, but when it comes down to it, I can't figure out where "rights" derive from. What's the first principle that says anyone has a "right" to anything? That's not to say I don't believe in civil rights as a just cause, or that human rights should be upheld, I just think they are a construct of sentient beings...not endowed by a creator or by nature. Utilitarianism has some reasonable answers on the question of rights, among other things.

I understand the discomfort people feel in comparing humans to animals, but I found it challenging in a good way. I've always had serious doubts about the arguments people make about humans being unique; I haven't believed in a soul since I was a child. So, Singer's arguments, even the uncomfortable ones, weren't such a huge leap.