Tutorial #10. Kripke on Names. Some Consequences

---> Essentialism
+ Essential property: a property an object (or kind) cannot fail to have.
- Example: being a football player is not essential to Ronaldo but being human is essential to him.
- Example: Water is H2O. There could be a colorless, tasteless liquid that was just like water, and also called 'water' by people, but with molecular structure XYZ. Then, that liquid would NOT be water: The essence of water is it’s molecular structure (H2O).

+ What about what seem to be contingent identity statements involving rigid designators?
E.g.
- 'Hesperus is Phosphoros.'
- 'Heat is the total energy of molecular motion.'

Kripke: The alleged contingency of both these sentences is an illusion!
They are a posteriori but necessary. The illusion comes from confusing necessity and a prioriticity!

--> How are contingent identity statements possible?
Everything that exists is necessarily self-identical.
Referring expressions in some identity statements pick out different objects at different possible worlds.