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The Identity of Indiscernables

The Identity of Indiscernibles (hereafter called the Principle) is usually formulated as follows: if, for every property F, object x has F if and only if object y has F, then x is identical to y. Or in the notation of symbolic logic:

∀F(Fx ↔ Fy) → x=y.

Or, in more prosaic terms: If two objects share exactly the same set of properties, then they are the same thing.

Referenced in

On the Ambiguity of "Content Type"

Leibnitz’s principle of the identity of indiscernibles applies to entity types. That means entities P and Q are the same entity type if every attribute possessed by P is also possessed by Q.