Full Idea
We can distinguish between numerical identity and qualitative identity. Numerical sameness is explained by a theory of identity, but what explains qualitative sameness?
Gist of Idea
Numerical sameness is explained by theories of identity, but what explains qualitative identity?
Source
Cynthia Macdonald (Varieties of Things [2005], Ch.6)
Book Reference
Macdonald,Cynthia: 'Varieties of Things' [Blackwell 2005], p.219
A Reaction
The distinction is between type and token identity. Tokens are particulars, and types are sets, so her question comes down to the one of what entitles something to be a member of a set? Nothing, if sets are totally conventional, but they aren't.