Beliefs in the impossibility of interpersonal comparison of welfare and the unacceptability of utilitarianism are based on a non-materialist solution to the theory of mind, i.e. on the existence of a soul. The compellingness of the theory of evolution and some discoveries in brain sciences render (philosophical) materialism very persuasive. The acceptance of materialism implies the negation of free will, non-significance of the self (no substantial reason to care much more about the welfare of one's own future self than the welfare of others), possibility of interpersonal comparison of welfare, compellingness of utilitarianism, and the possibility of conscious machines. Searle's argument on the impossibility of rigorous social sciences is however rejected.