 Personhood. What is it to be a person, as opposed to a nonperson? What have we people got that nonpeople haven’t got? More specifically, we can ask at what point in our development from a fertilized egg there comes to be a person, or what it would take for a chimpanzee or a Martian or an electronic computer to be a person, if they could ever be. An ideal account of personhood would be a definition of the word person, taking the form ‘Necessarily, x is a person at time t if and only if … x … t …’, with the blanks appropriately filled in. The most common answer is that to be a person at a time is to have certain special mental properties then (e.g. Baker 2000: ch. 3). Others propose a less direct connection between personhood and mental properties: for example that to be a person is be capable of acquiring those properties (Chisholm 1976: 136f.), or to belong to a kind whose members typically have them when healthy and mature (Wiggins 1980: ch. 6).