Questions: Sortal Concepts and Identity Conditions

Question 1

A ship has all its planks gradually replaced over 20 years. The original planks are then reassembled into a ship elsewhere. Which is the original ship?

• A. The continuously operating ship — it maintained functional and social continuity throughout
• B. The reassembled ship — identity follows matter, and the original matter defines the original object
• C. The answer depends on which identity criterion the sortal 'ship' imposes — the puzzle has no sortal-neutral resolution
• D. Neither is the original ship, because ships cannot persist through material change

Answer: (C)

This is the Ship of Theseus puzzle. Under an artifact sortal with functional/social continuity criteria, the operating ship is the same ship. Under a material constitution criterion, the reassembled ship has the stronger claim. The point is that 'which is the original ship?' cannot be answered without first settling what makes ships the same ship over time — that is, without specifying the identity conditions your sortal imposes. Different criteria yield different verdicts, and neither is automatically correct.

Question 2

After severe brain surgery, a person has complete psychological discontinuity — no memories, radically different personality. Applying Locke's psychological continuity criterion for persons versus the biological organism sortal gives which result?

• A. Both sortals agree: this is the same person, because the same body is present
• B. Both sortals agree: this is a different person, because personality has changed
• C. Under the 'person' sortal (psychological continuity), it may not be the same person; under 'organism,' it is the same animal
• D. Sortal analysis is irrelevant — neuroscience settles what counts as the same person

Answer: (C)

The same physical entity can be assessed by different sortals with different verdicts. Under Locke's person sortal (memory and psychological connectedness as the criterion), complete discontinuity means the person may have ceased. Under the biological organism sortal, the same animal persists because bodily continuity is unbroken. This is not a contradiction — it shows that 'same X' is sortal-relative. The question 'Is this the same person?' and 'Is this the same organism?' are different questions with potentially different answers.

Question 3

Two different sortals can apply to the same physical entity at the same time and yield different verdicts about whether it has persisted through a change.

• T. True
• F. False

Answer: True

Yes — this is precisely the force of sortal-relative identity. A human being is simultaneously a person and an organism. If that person undergoes complete psychological discontinuity, the 'organism' sortal says continuity is preserved (same biological animal), while the 'person' sortal (on Lockean grounds) says continuity is broken. The physical facts are the same; the identity verdict differs because the sortal determines what counts as persistence.

Question 4

Because identity is a logical relation (nearly every thing is identical to itself), the question 'Is this the same X?' usually has a determinate, sortal-independent answer.

• T. True
• F. False

Answer: False

Logical identity (a = a) is sortal-independent, but persistence questions — 'Is this the same X across time and change?' — are not. The logical fact that a thing is self-identical doesn't settle whether a changed entity is the same instance of some kind. That question requires criteria for what counts as persistence under that kind, which is exactly what sortals provide. Without specifying the sortal, 'same X' is indeterminate — not because logic fails, but because identity-over-time is a substantive question, not a logical tautology.

Question 5

What does it mean to say that identity is 'sortal-relative,' and why does this matter for puzzles like the Ship of Theseus?

Model answer: Saying identity is sortal-relative means that 'Is this the same X?' can only be answered once you specify the kind X — because different kinds impose different criteria for what counts as persistence. For 'ship,' the criterion might be functional/social continuity (favoring the operating ship) or material constitution (favoring the reassembled ship). Neither criterion is built into reality independently of the sortal. The Ship of Theseus puzzle appears paradoxical because we implicitly assume there must be a sortal-neutral fact of the matter, but there isn't — the puzzle dissolves once you recognize that different sortals license different answers.

Sortal-relative identity also explains why identity puzzles in law, personal identity, and metaphysics resist simple resolution: they often involve competing sortals (legal person vs. biological organism, artifact vs. pile of material) without a principled way to adjudicate which sortal takes precedence.