It is difficult to use physical sameness to justify the sameness of a person. Pepole can lose limbs and still be considered the same being. Locke proposes a better definition of sameness of two human beings: a body persists personhood if it sustains a single uninterrupted life. Simply being the same human being does not imply the same person though. If a human being has multiple personality disorder, then someone may be justified in thinking that they are different people. Justifying two persons as being the same requires determining the substance of a person, which is arguably the experiences we possess.
In Locke’s view, psychological connectedness is necessary and sufficient to justify the sameness of a person. Locke holds the view that a person consists of a thinking thing (Cartesian idea of the mind). As such, two persons are the same if they hold the same consciousness. Two persons are said to have the same consciousness if there is a “strong relation of psychological continuity between them”, which is to say that they share much of the same memories.
This view on the sameness of person is both necessary and sufficient
- Necessity: If one cannot remember anything about his past, then his new self was markedly a different person than his past self.
- Sufficiency: Reincarnation persists personhood. If a person is a reincarnation of a dead person and possesses the dead person’s memories, ideas, etc, then they can be considered the same person.
Possible issues of this view include:
- Are we strongly psychologically connected to our past by transitivity? Memory can fade easily, so if we forget about much of the past, did we become a different person.
- Does forgetting an action absolves oneself of the moral consequences?