Who are you? Who am I? Are we persons and if we are, are we the same persons we were yesterday? What does our being persons consist in? These are the sorts of questions philosophers try to answer on the nature of personal identity, the persistence question. The persistence question is often considered the question of personal identity: what are the conditions under which a person who exists at time t1 is identical to a person who exists at time t2?
There are two approaches to answering the persistence question, the complex view and the simple view.
Philosophers who accept the complex view aim to provide informative, non-trivial necessary and sufficient conditions for identity, be these biological or psychological conditions. The biological approach falls broadly into two camps: animalism, and the brain-based approach. A bodily (biological) criterion of personal identity holds that I am a past or future being that has my body, or that is the same biological organism that I am. I am the same person I was yesterday because I have biological continuity.
Eric Olson’s animalism (laid out in his book, The Human Animal) is a brute-physical view. We are (human) animals and have the same persistence conditions as non-human animals: being a person is a property some animals have some of the time. A common objection to animalism is that if your brain was transplanted into another body you would be left behind while your cerebrum was transplanted, yet it seems intuitive that the resulting person would be you – she would have your memories, personality, and other mental properties and features. The resulting person would be psychologically continuous with you yet brute-physical persistence conditions suggest the empty-headed being left behind would be you.
Another physicalist view is the brain-based approach, which claims that the person is identical to the brain or some part of it. The brain, or relevant part of the brain, produces the psychological states and mental life characteristic of being a person, and damage to the brain can result in personality changes and memory loss. Contrast this with the animalist view for which personal identity obtains in the organism, and for whom having a mental life has no bearing on personal identity over time.
Psychological continuity approaches are complex views but rule out our being organisms. In a brain transplant scenario, the being who received your brain would be psychologically continuous with you, having your memories and personality. The empty-headed being left behind looks like you but does not have your mental features. A physicalist objection is that psychological accounts of personal identity obscure the ways in which we recognise other persons. When I arrive in class and my friends greet me they do so because they recognise a being, an organism, Kerrie. They do not recognise a consciousness, nor a continuous psychology.
Defenders of the simple view argue that personal identity is fundamentally basic, and as such cannot be broken down into more basic psychological or biological parts. Personal identity is a simple relation, while psychological and biological relations are epistemic criteria for justifying personal identity but they are not personal identity itself. Personal identity does not obtain in material or non-material relations; it does not exist outside itself, and has the power to persist through time. Whatever a person is, is not dependent on properties or substances for its identity. A person can change qualitatively yet retain their identity.
A new wrinkle in this debate is owed to Lynne Rudder Baker: the not-so-simple simple view of personal identity. Baker identifies persons with “the first-person perspective”. The answer to the question “who am I?” is that I am the perspective I have of myself, and my persistence conditions are first-personal. Persons are not identified with biological or psychological properties but with a particular “robust, first-person perspective”. In Baker’s words, “To be a person is to have a first-person perspective essentially, and a person continues to exist as long as her first-person perspective is exemplified.” But an objection raised to Baker’s not-so-simple simple view of personal identity is that it is circular.
Metaphysical questions of personal identity continue to be asked by philosophers, but it seems to me that in asking these questions we should not lose sight of what our personal identity means to us. As our lives follow their trajectory, our memories, our relationships and our sense of ourselves and the unfolding of our lives are what matter to us. Personal stories from dementia patients and their carers testify to the fear of not being “the same person”. As Marya Schechtman notes: “Our understanding of where we were born, where we lived, who we lived with, and the basic circumstances of our youth all become part of our adult narratives… People who do not have this information usually feel as if they are lacking something important.”