Singer has argued against the permissibility of killing people (and certain animals) on the grounds of the distinction between conscious and self-conscious animals. Unlike conscious animals, which can be replaced without a loss of overall welfare, there can be no substitution for self-conscious animals. In this article, I show that Singer's argument is untenable, in the cases both of the preference-based account of utilitarianism and of objective hedonism, to which he has recently turned. In the first case, Singer cannot theoretically exclude that a self-conscious being's stronger preferences may only be satisfied by killing another self-conscious being. In the second case, he fails to demonstrate that the rules of ordinary morality, demanding that killing be strictly forbidden, could not frequently be overruled by the principles of esoteric morality. In both cases, his theory cannot solve the classical utilitarian problem of prohibiting the killing of people in secret.