Identity
Identity: the relation that a thing bears only to itself.
Gottfried Wihelm Leibniz says:
Indiscernibility of identicals: if any two things are identical, then they must share all the same properties.
The Ship of Theseus lost its identity once the first plank was replaced.
Essential property vs accidental properties
Essential properties: core elements needed for a thing to be the thing that it is.
Accidental properties: traits that could be taken away from an object without making it a different thing.
Heraclitus said “you cannot step in the same river twice.”
Fungibility: the property of being interchangeable with other objects of the same kind.
Personal Identity
Body theory: personal identity persists over time because you remain in the same body from birth to death.
John Locke considered the thing that makes you is your consciousness. He proposed:
Memory theory: personal identity persists over time because you retain memories of yourself at different points, and each of those memories is connected to one before it.
Does people with dementia still be the same person?
David Hume argued that
The idea of the self doesn’t persist over time. There is no you that is the same person from birth to death.