Full Idea
Identity is a primitive notion.
Gist of Idea
Identity is primitive
Source
David Wiggins (Sameness and Substance [1980], 2.1)
Book Reference
Wiggins,David: 'Sameness and Substance' [Blackwell 1980], p.49
A Reaction
To be a true primitive it would have to be univocal, but it seems to me that 'identity' comes in degrees. The primitive concept is the minimal end of the degrees, but there are also more substantial notions of identity.