Cases exist where, despite knowing all other relevant facts, determining personal identity remains elusive.
These scenarios fall outside the scope of conventional personal identity criteria.
The question is whether such cases pose a significant problem.
While some argue these cases are purely hypothetical, Parfit suggests their potential, even if unrealized, warrants consideration.
Parfit challenges two core beliefs:
The belief that identity questions must always have a definitive answer.
The belief that identity is crucial for addressing survival, memory, and responsibility.
He argues that questions about identity can be separated from important related questions.
The Amoeba Case
Wiggins presents the case of a person dividing, similar to an amoeba.
Shoemaker's operation: Brain transplantation into another body results in the recipient exhibiting the original person's characteristics and memories; most would consider this survival.
Wiggins' operation: The brain is divided, and each half is transplanted into a new body, with each resulting person having the original person's characteristics and memories.
Three possible outcomes:
The original person does not survive.
The original person survives as one of the two.
The original person survives as both.
Objection to (1): Inconsistent, given the possibility of surviving a successful whole-brain transplant or surviving with half a brain destroyed.
Objection to (2): Since each resulting person is initially identical, there's no basis for choosing one over the other as the survivor.
Description (3): Survival as both; possibly resulting in a divided mind across two bodies.
Divided Minds
It's conceivable to have a divided mind with simultaneous, mutually unaware experiences.
Evidence comes from cases where the brain hemispheres are surgically separated to treat epilepsy, creating "two separate spheres of consciousness." According to the surgeon.
Imagine controlling the connection between brain hemispheres voluntarily, allowing for a divided mind at will.
Example: During a math exam, dividing the mind to solve a problem using two different methods simultaneously, then reuniting to compare answers.
Experience during division: Consciousness splits, but each stream seems continuous with the original, except for sensory and motor control loss on one side.
Each stream is unaware of the other's activity but remembers assigning tasks to each hand.
After reunification, there's a sudden recollection of working on two calculations independently.
If the mind can be divided, a person's mental history can resemble a river with multiple streams rather than a single canal.
Wiggins' operation may lead to two bodies and a divided mind, which isn't absurd but unsatisfactory.
The exam scenario suggests a temporary division within one person because the mind is reunited and there's only one body.
In Wiggins' case, the permanent division and two separate bodies blurs the concept of a single person.
The resulting individuals possess all the attributes of a person and could live independently, making it difficult to deny their separate identities.
Even if they are different people, one might argue that the original person survives as both, implying identity.
This could mean two people compose a third, akin to the Pope's three crowns forming one crown.
However, this alters the conventional concept of a person.
Parfit suggests abandoning the language of identity and accepting that the original person survives as two different people without being identical to either.
Challenging Beliefs About Identity
The idea that questions about personal identity must have a true answer in every case.
Wiggins' case reveals the implausibility and triviality of this belief.
It is like asking if England is the same nation after 1066 and realizing that there is no clear answer.
The belief that important questions hinge on identity.
Parfit argues that while some questions presuppose identity; they can be rephrased to remove this dependence.
Once freed from the constraints of identity, these questions retain their significance.
Survival and Identity
The question "Will I survive?" is often considered equivalent to "Will there be someone alive who is the same person as me?"
If treated as equivalent, the least problematic description of Wiggins' case is surviving with two bodies and a divided mind.
Some argue that the original person is neither of the resulting individuals, implying non-survival and equating Wiggins' operation with death.
This view is flawed, as attitudes should be consistent and based on true beliefs.
Criticism arises if one believes the relation to each resulting person lacks an element of survival, despite agreeing that the relation to one person would constitute survival.
Duplication alone shouldn't negate survival; it's like rejecting a drug that doubles lifespan out of inconsistency.
For those who believe in a true answer, multiplying could be a way to lose identity rather than dying, confusing zero with two.
Those who see identity as a matter of decision would find it absurd to consider Wiggins' operation as death, given they could choose to identify with one of the resulting people.
The relation of the original person to each resulting person contains all that is of interest in survival.
A sense is needed in which one person can survive as two.
Identity as a One-to-One Relation
Identity is a one-to-one relation, but what matters in survival need not be.
Wiggins' case illustrates that the relations which matter are, in fact, one-one.
Identity is all-or-nothing, whereas what matters in survival are relations of degree.
Ignoring this distinction leads to ill-grounded attitudes and beliefs.
Psychological continuity (including causal continuity) can be used to imply identity.
Williams argues that psychological continuity cannot provide a criterion for identity since identity is one-one, and psychological continuity is not logically one-one.
Psychological continuity is a ground for speaking of identity when one-one.
If psychological continuity branched, the language of identity would need to be abandoned.
Judgments of personal identity are important because they imply psychological continuity.
Williams' principle states that an important judgment should be asserted and denied only on importantly different grounds.
In cases of branching psychological continuity, the importance of identity should be attached directly to each limb of the branching relation.
Even if psychological continuity is not always one-one, it can provide a criterion of identity.
A criterion for identity is: "X and Y are the same person if they are psychologically continuous and there is no person who is contemporary with either and psychologically continuous with the other."
If psychological continuity branches, we should speak in a new way, regarding what we describe as having the same significance as identity.
Memory and Identity
A sense of "survive" which does not imply identity is needed.
Most of what matters in survival are relations of degree.
None of these relations needs to be described in a way that presupposes identity.
The relation involved in memory is crucial, as it's easy to believe its description must refer to identity.
It may be a logical truth that we can only remember our own experiences, but we can frame a new concept for which this is not a logical truth: "q-memory".
I am q-remembering an experience if:
I have a belief about a past experience that seems like a memory belief.
Someone did have such an experience.
My belief depends on this experience in the same way a memory does.
According to (1), q-memories seem like memories, so I q-remember having experiences.
When I seem to remember an experience, I seem to remember having it, but it's automatically assumed that I am the person who had this experience.
If I started having q-memories of other people's experiences, I would cease to assume that my apparent memories must be about my own experiences.
My apparent memories would now come to me as q-memories.
Wiggins' case illustrates this, as the resulting people have apparent memories of living the original person's life and regard these as only q-memories.
Every memory is also a q-memory; memories are simply q-memories of one's own experiences.
We could drop the concept of memory and use q-memory instead, describing the relation between an experience and a "memory" of it without presupposing they are had by the same person.
This vindicates the "memory criterion" of personal identity against the charge of circularity and may help with the problem of other minds.
Intentions and Identity
Intentions can be redescribed as q-intentions, and one person could q-intend to perform another person's actions.
In Wiggins' case, the original person can q-intend to perform the actions of the resulting people.
The phrase "q-intend as one of them" reminds us we need a sense in which one person can survive as two.
The concepts of q-memory and q-intention provide a model for others: a man who can q-remember could q-recognize, and be a q-witness of, what he has never seen; and a man who can q-intend could have q-ambitions, make q-promises, and be q-responsible for.
Many different relations are included within, or are a consequence of, psychological continuity.
These relations are described in ways that presuppose the continued existence of one person, but they could be described in new ways that do not.
It might be possible to think of experiences in a wholly "impersonal" way.
A way of thinking of our own identity through time which is more flexible, and less misleading may be used which allows for a sense in which one person can survive as two; it also treats survival as a matter of degree.
Fusion
Fusion shows that what matters in survival can be a question of degree.
Fusion involves two people coming together physically, and their bodies growing into one while they are unconscious.
The resulting person can q-remember living the lives of the two original people.
Some things must be lost, as the two original people will have different characteristics, desires, and intentions.
Some of these will be compatible and can coexist in the one resulting person, while some will be incompatible and may cancel out or weaken each other.
Someone about to fuse can have intentional control over the actions of the resulting individual.
The choice of a partner for fusion can be well-considered.
Fusion, while not clearly survival, is not clearly failure to survive.
What matters in survival can have degrees.
Natural Division
Imaginary beings that reproduce by natural division.
The lines on the diagram represent the spatiotemporal paths which would be traced out by the bodies of these beings.
Each single line is referred to as a "branch".
Each "branch" corresponds to what is thought of as the life of one individual.
A's relation to both B + 1 and B + 2 is just as good as survival.
Psychological continuity has been provisionally referred to earlier as what matters in survival.
A distinction must now be made between this relation from another, which shall be called "psychological connectedness."
The relation between a q-memory and the experience q-remembered is a "direct" relation.
Another "direct" relation is that which holds between a q-intention and the q-intended action.
A third is that which holds between different expressions of some lasting q-characteristic.
"Psychological connectedness" requires the holding of these direct psychological relations.
Connectedness is not transitive, since these relations are not transitive.
“Psychological continuity” only requires overlapping chains of direct psychological relations, which results in "continuity" being transitive.
A is psychologically continuous with B + 30 but need not be psychologically connected to B + 30.
Connectedness requires direct relations.
Q-memories will weaken with the passage of time, and then fade away, and Q-ambitions will be replaced and Q-characteristics changed.
Connectedness is a more important element in survival.
Descendant Selves
A can think of any individual, anywhere in his "tree," as "a descendant self."
This phrase implies psychological continuity.
Any later individual can think of any earlier individual on the single path which connects him to A as "an ancestral self."
Since psychological continuity is transitive, "being an ancestral self of" and "being a descendant self of" are also transitive.
The phrases "one of my future selves" and "one of my past selves" imply psychological connectedness.
These phrases are used to describe Wiggins' case.
The original person survives Wiggins' operation: the two resulting people are his later selves.
Since psychological connectedness is not transitive and is a matter of degree, the relations "being a past self of" and "being a future self of" should themselves be treated as relations of degree. This leads to a series of descriptions: "my most recent self," "one of my earlier selves," "one of my distant selves," "hardly one of my past selves (I can only q-remember a few of his experiences)," and, finally, "not in any way one of my past selves just an ancestral self."
Fusion and Division
Hypothetical beings reproduce by fusion every autumn and divide every spring.
For them, phrases like "an ancestral self" and "a descendant self" would cover too much, and the word "I" would cover too little, necessitating more talk about past and future selves.
A theoretical flaw is that the phrase "a past self of" implies psychological connectedness and that this connectedness may vary in degree within a single life.
Everlasting Bodies
Hypothetical world with neither division nor union but everlasting bodies that gradually change.
Direct psychological relations hold only over limited periods of time.
Such beings could regard themselves as immortal because the parts of each "line" are all psychologically continuous but not all psychologically connected.
To improve thinking, the distinction between successive selves connects to the degrees of psychological connectedness.
Because this connectedness is a matter of degree, the speaker can choose whether to apply a label from context to context.
The word "I" is used to imply the greatest degree of psychological connectedness.
When connections reduce, such as when there is any marked change of character or style of life, or any marked loss of memory, these beings would say, "It was not I who did that, but an earlier self."
Final Thoughts
What matters in the continued existence of a person are, for the most part, relations of degree.
The principle of self-interest has no force.
The principle of biased rationality entails doing what will best achieve what you actually want.
The principle of impartiality entails doing what is in the best interests of everyone concerned.
Egoism, fear of distant death, and regret are all strengthened by beliefs about personal identity.
Weakening these emotions can be achieved by giving up these beliefs, though it may come at the cost of weakening positive emotions such as loyalty.