We often talk and behave as if being a man required more than just being male, and being a woman required more than just being female. There are expectations that need to be met if someone wants to fully qualify as a man or a woman in their social environment, expectations regarding their behaviour as well as character. It is, however, not entirely obvious what ‘being a man’ or ‘being a woman’ actually means and in what way and to what (...) extent it defines our identity, making us who we are. Would I be a different person if I were a woman? And what would it take for me to be a woman? Could I conceivably be neither? Or both? If gender were nothing but sex, telling a man to ‘be a man’ would make little sense. We may have different ideas about what it means to be a man or woman and how we need to behave in order to secure or maintain our manhood or womanhood, but we are all likely to have some deeply ingrained understanding of what makes a man a man and a woman a woman that goes beyond mere biology. Does it, however, follow that gender can, if necessary or desired, be completely detached from sex, that I can be a woman despite having all the physical attributes of a male member of my species, or a man despite being biologically female? If so, on what grounds exactly would we decide who is what? (shrink)