Abstract: Ethical theory seeks to offer principled answers to normative questions. It often starts with our intuitions about particular cases, and tries to uncover the general principles that underlie them. Work on so-called ‘trolley problems’ is a paradigmatic example of this method. But ethicists are no longer the only ones chasing trolleys: in recent years, psychologists and neuroscientists have also turned to study our moral intuitions and what underlies them. What is striking is that scientists are now investigating the very same thought experiments and intuitions, and sometimes even proposing the same underlying principles. In this talk, I aim to clarify the relation between these two inquiries. How can they seem so similar, if ethical theory is an armchair inquiry into moral truth, and psychology (and neuroscience) an empirical inquiry into causal mechanisms? Should we expect the underlying principles identified by the two inquiries to converge? Does it matter to ethics whether or not they do? I argue that reflection on these questions can help uncover psychological assumptions that are implicit in ethical theorizing. If my argument is correct, then psychology (and to a lesser extent neuroscience) will have a central positive role to play in future ethical theory.