Neuropsychologist Paul Broks asks how we can be sure we're the same person as we were yesterday. The philosopher John Locke thought it depended on what we could remember: if we could remember something happening to us, then we were the same person as the person it happened to. But is that true? What if our memories could be downloaded and then uploaded into another body? Would that new person be the same as us? And if so, how much would we care if the body we now inhabit was destroyed? These sci-fi philosophical thought experiments can make us rethink our concept of personal identity and maybe even our attitudes towards death. In the end, is there really a self at all, or are we just a bundle of mental states and events? Presenter: Paul Broks Producer: Jolyon Jenkins.