Full Idea
Identity claims are only true if the entities referred to are of the same category, and meet the criteria of identity appropriate for things of that category.
Gist of Idea
Identical entities must be of the same category, and meet the criteria for the category
Source
Amie L. Thomasson (Ordinary Objects [2007], 03)
Book Reference
Thomasson,Amie L.: 'Ordinary Objects' [OUP 2010], p.57
A Reaction
This may be a little too optimistic about having a set of clear-cut and reasonably objective categories to work with, but attempts at establishing metaphysical categories have not gone especially well.
Related Idea
Idea 14476 Identity claims between objects are only well-formed if the categories are specified [Thomasson]