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Single Idea 14065

[filed under theme 9. Objects / F. Identity among Objects / 8. Leibniz's Law ]

Full Idea

For two things to be strictly identical, they must have all properties in common. That means, among other things, that they must start to exist at the same time and cease to exist at the same time.

Gist of Idea

Two identical things must share properties - including creation and destruction times

Source

Allan Gibbard (Contingent Identity [1975], I)

Book Ref

-: 'Journal of Symbolic Logic' [-], p.188

A Reaction

I don't accept that coming into existence at time t is a 'property' of a thing. Coincident objects give you the notion of 'existing as' something, which complicates the whole story.

The 14 ideas from Allan Gibbard

14064 If a statue is identical with the clay of which it is made, that identity is contingent [Gibbard]
14066 A 'piece' of clay begins when its parts stick together, separately from other clay [Gibbard]
14067 Clay and statue are two objects, which can be named and reasoned about [Gibbard]
14065 Two identical things must share properties - including creation and destruction times [Gibbard]
14070 A particular statue has sortal persistence conditions, so its origin defines it [Gibbard]
14069 We can only investigate the identity once we have designated it as 'statue' or as 'clay' [Gibbard]
14071 Naming a thing in the actual world also invokes some persistence criteria [Gibbard]
14072 Possible worlds identity needs a sortal [Gibbard]
14073 Claims on contingent identity seem to violate Leibniz's Law [Gibbard]
14074 Leibniz's Law isn't just about substitutivity, because it must involve properties and relations [Gibbard]
14076 Essentialism is the existence of a definite answer as to whether an entity fulfils a condition [Gibbard]
14077 Essentialism for concreta is false, since they can come apart under two concepts [Gibbard]
14078 Only concepts, not individuals, can be the same across possible worlds [Gibbard]
14079 Kripke's semantics needs lots of intuitions about which properties are essential [Gibbard]