The last decades of the twentieth century saw the rise of modern genetics. Now, many regard the initial decades of the twenty-first century as an era that promises explosive growth in our knowledge of the brain. Just as ethical issues have been a part of discourse in genetics from the outset, we are now paying attention to ethics in neuroscience. But whereas the ethics of genetics was in many ways a new conversation, the philosophical discussion of mental function and behaviour is an ancient tradition that both informs and complicates the emerging field of neuroethics.