Is there something about the life of a rational and self-conscious being, as distinct from a being that is merely sentient, that makes it much more serious to take the life of the former than the latter? One line of argument for giving an affirmative answer to this question runs as follows. A self-conscious being is aware of itself as a distinct entity, with a past and a future. (This, remember, was Locke's criterion for being a person.) A being aware of itself in this way will be capable of having desires about its own future.
