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Sunday, January 08, 2017

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Fortunately this is purely a question of logic, with minimal philosophical content.

>>if two putatively distinct entities are in fact numerically the same entity, then the names for these putatively distinct entities are co-referential: they designate one and the same entity.

Simplifying, where n(name, bearer) is the naming function:

Principle: (x)(y) [ x=y & n(‘x’,x) -> n(‘x’,y) ]

Thus
1. a=b
2. n(‘a’,a)
3. n(‘a’,b)

The move from 2 to 3 invokes your principle. Note the substitution of ‘b’ for ‘a’.

>>I don't see the need to invoke a principle of substitutivity. In the above inference there was no substitution of a name for a name.

But your inference involved the principle I formalised above, which is a specific instance of the principle of substitutivity. This does indeed require the substitution of a name for a name.

To win this game you need to formalise what you said above in a way that does not invoke substitutivity.

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