Could a species possibly be without a moral sense yet sapient, or does morality follow directly from sapience?
UPDATE: The most obvious problem of all is the epistemological question: how do we really know whether any other beings are really sentient or sapient? This section in Wikipedia describes the philosophy and problems fairly well.
I've just learned that sentience and sapience are actually quite distinct concepts, with the former not implying self-awareness and the latter implying it. It's left me a bit confused. Regardless, Singer uses sentience: if they have nerve endings which transmit pain signals to the brain, then they are sentient (many animals -- how about starfish and sponges?). If they don't, then they don't suffer. If they do suffer, we need to minimize their suffering (to what degree?). Singer seems to ignore the relevance of "sapience" as I've described it, but I'm not so sure that that is a good path.
Anyway. I need to do some late-night grocery closes.