 One of the aspects of neuroethics that makes it distinctive and importantly different from traditional bioethics is that we recognize that, in some yet-to-be-articulated sense, the brain is the seat of who we are. For example, we now have techniques that alter memories by blunting them, strengthening them, or selectively editing them. We have drugs that affect sexuality, and others that affect mood. Here, neuroethics rubs up against some of the most challenging and contentious questions in philosophy: What is the self? What sorts of changes can we undergo and still remain ourselves? What is it that makes us the same person over time? Of what value is this temporal persistence? What costs would changing personhood incur?