Entrenched in the “simple” view is the idea that personal identity, and the persistence of personal identity, cannot be measured through philosophical discourse or scientific investigation. There are a number of opposing arguments, known as complex theories of personal identity. In each of these arguments, the central claim is that either the body, the brain, or the psychological continuity of an individual determines how they persist as the same person (Garrett, 1998, p 52). To call them complex is a misnomer – for each is far too narrow to properly define and explain personal identity.
Complex argument 1– Psychological continuity
John Locke defines a person as a ‘thinking, intelligent being, that has reason and reflection and can consider itself as itself, the same thinking thing, in different times and places’ (Locke, 1689, p 1-6). This statement suggests that, in order to persist as the same person, we must have a mental consciousness which persists through time. We can say that a person is psychologically continuous if they have a mental state that is descendent from their previous mental states. For example, this theory states that a five-year-old will be the same person when they are a 25-year-old, because their mental state in later years is descendent from their earlier years.
By its very nature, the idea of psychological