A case of acting out in a borderline patient is reported to demonstrate that, in addition to all the other well-known factors contributing to this phenomenon, preservation of identity is an important element. In borderline cases, where fear of loss of identity represents an ever-present danger, acting out may be resorted to as a derivative of that phase in which locomotion was brought into

the service of supporting separation from the mother, and where the gratification of action led to the experiencing of self as an autonomous person.