Hedden, Rationality and Synchronic Identity Flashcards
What is the central question of Hedden’s paper?
How should rationality account for cases where it’s unclear whether conflicting mental states belong to one rational subject or multiple ones? Hedden explores the individuation of rational subjects at a single time (synchronic identity) and proposes a pluralist view of rational subjecthood.
What is “synchronic identity”?
Identity at a time, as opposed to diachronic identity (identity over time). It is crucial for rational requirements like consistency—because contradictory beliefs are irrational only if they belong to the same rational subject at that time
What is a “rational subject”?
The kind of entity that is subject to rational requirements and the target of rational evaluation—whether they have consistent beliefs, rational preferences, etc.
What is the “Even and Odd” case (Multiple Personality)?
A fictional being with two personalities that alternate every day. Each has distinct beliefs and no memory of the other’s thoughts. Raises the question: Is this one irrational subject with inconsistent beliefs, or two separate rational subjects?
What is significant about split-brain patients?
Their hemispheres act semi-independently—e.g., one hand picks up a toothbrush, the other a pencil. Shows mental disunity, challenging whether they are one or multiple rational agents.
Who are Krista and Tatiana Hogan?
Conjoined twins at the head, possibly sharing phenomenal experiences via a brain connection. They may blur the line between one and two rational subjects.
How does the octopus challenge rational unity?
Octopuses have decentralized nervous systems. Their arms act independently but also respond to visual cues. They exhibit both central and local control, complicating rational subjecthood.
What is Lewis’s case of “fragmentation”?
He holds inconsistent beliefs about Princeton’s geography. Rather than being fully irrational, his mental states are split into coherent fragments that don’t operate simultaneously. Raises the idea of fragmented rational subjecthood.
Organismic Criterion
What is the organismic criterion?
A: Two mental states belong to the same rational subject if they are realized in the same organism (e.g., same body). Common-sense default.
What are its problems?
A: Fails in:
Craniopagus twin cases (possibly one organism, but two minds).
Cerberus (mythical two-headed dog): intuitively has two agents, but counts as one organism.
Psychological Criterion
What is the psychological criterion of rational subjecthood?
A: Mental states belong to the same subject if they are causally interconnected in a mental system.
What are its issues?
A: It’s vague: How much connectedness is enough? It risks:
Counting Hogan twins as one subject.
Counting Lewis’s belief fragments as separate subjects. Also, mental systems don’t themselves believe/desire, which creates metaphysical tension.
Self-Conception Criterion
What is the self-conception criterion?
A: Two mental states belong to the same subject if they are tied to an entity that has self-referential thoughts or a commitment to rational unity.
What’s wrong with this view?
It may be circular (e.g., using ‘I’ doesn’t guarantee subjecthood).
Rationality can apply to entities lacking self-conception, like simple AI or nonhuman animals.
What is Hedden’s pluralist view of rational subjecthood?
There are many rational subjects in any scenario—parts, wholes, and sums of organisms. For any set of mental states (with minimal constraints), there exists a rational subject who has exactly those states.
What are the two key constraints of Hedden’s pluralist view?
- If two mental states are realized by the same physical matter, they can’t belong to different rational subjects.
- A rational subject must exist as a physical object composed of the matter realizing the mental states.
What is mereological universalism, and how does it relate to Hedden’s pluralism?
Mereological universalism holds that any group of objects forms a composite object. Likewise, Hedden says any group of mental states (realized in existing matter) forms a rational subject. We ignore most of them pragmatically, but they exist.
PRAGMATIC REASONS TO FOCUS ON SOME SUBJECTS
Q: Why should we attend only to some rational subjects?
Because of our practical purposes—prediction, explanation, and criticism. For example:
- Split-brain studies: it’s useful to focus on each hemisphere.
- Cerberus: each head should be treated separately.
- Hogan twins: better to assess each individually than the sum.
What are the roles of rational evaluation language?
- Prediction and explanation: We predict based on what agents rationally ought to do.
- Criticism and guidance: We evaluate to influence and improve others’ rational coherence.
How does this connect to Hedden’s rejection of diachronic rationality (from earlier work)?
Just as puzzle cases over identity across time led Hedden to reject diachronic requirements, synchronic puzzles raise the need for a pluralist theory of rational identity at a time—instead of rejecting synchronic rationality altogether.
What is Hedden’s conclusion about synchronic rationality?
Synchronic requirements must stay, but we need a pluralist and pragmatic way to apply them. Rational subjects are many, and which ones we attend to depends on contextual purpose.
How does this affect the debate on rationality overall?
It shifts focus from metaphysical debates about the identity of persons to a more flexible, purpose-driven account of rational evaluation. It also opens the door to rethinking diachronic rationality using similar pluralism.
