Theories of personal identity attempt to explain what makes a person the same person over time. What is it that ensures that I am the same person now as I was many years ago?
The two main approaches to personal identity propose criteria based on bodily continuity and on psychological continuity respectively. What makes a person the same person over time is thus taken to be the fact their body, or their mind, persists through time.
An alternative view, however, denies that there is a self that exists over time. Bundle theory holds that we are nothing more than a collection of mental states example, that there is no self over and above these mental states that possesses them.