Frankly, I think only sentient beings can have ultimate moral value. Other things can have it only instrumentally. However, the matter is a little more complicated than that. I will argue my view here.
“Sentient” means having inner experience, being able to feel something. As far as I can see, there is good reason to think that animals with a sufficiently complicated nervous system — and it doesn’t have to be very complicated — all have sentience, and other things don’t. It’s not really a question of whether the thing is an animal specifically or whether it has just what we call a nervous system, but you need something like that, and the only thing we know of at the moment that seems to fit are animals.
Sentience apparently implies the capacity to feel something like pleasure and pain, to experience things as positive or negative. As I see it, that is the core of moral value. Continue reading