Ideas from 'Identity' by John Hawthorne [2003], by Theme Structure

[found in 'Metaphysical Essays' by Hawthorne,John [OUP 2002,0-19-929124-1]].

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9. Objects / F. Identity among Objects / 1. Concept of Identity
Our notion of identical sets involves identical members, which needs absolute identity
                        Full Idea: Our conceptual grip on the notion of a set is founded on the axiom of extensionality: a set x is the same as a set y iff x and y have the same members. But this axiom deploys the notion of absolute identity ('same members').
                        From: John Hawthorne (Identity [2003], 3.1)
                        A reaction: Identity seems to be a primitive, useful and crucial concept, so don't ask what it is. I suspect that numbers can't get off the ground without it (especially, in view of the above, if you define numbers in terms of sets).