Equality compares which individuals fall under each concept. It does not require identical wording or the same role in a definition. In the book, “human” names a species while “rational” expresses an essential differentiating feature, yet their extensions coincide in the classical framework.
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Equal extensions need not mean identical definitions
Four Relations Between Universal Concepts
Equality compares which individuals fall under each concept. It does not require identical wording or the same role in a definition. In the book, “human” names a species while “rational” expresses an essential differentiating feature, yet their extensions coincide in the classical framework.