Problems with a constitution account of persons

There are some problems with Lynne Baker's constitution account of personal identity that become evident when we consider brain transplant thought experiments and two kinds of rare cases of conjoined twins-the first appears to be one organism but two persons and the second seems to involve two organisms associated with one person. To handle the problems arising from brain transplants, the constitution theorist must admit an additional level of constitution between the organism and the person. To resolve the problems posed by the two kinds of conjoined twins, the constitution theorist must accept that constitution is not always a one-to-one relationship.