more from Penelope Maddy

Single Idea 13014

[catalogued under 4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / b. Axiom of Extensionality I]

Full Idea

The extensional view of sets is preferable because it is simpler, clearer, and more convenient, because it individuates uniquely, and because it can simulate intensional notions when the need arises.


And example of an 'intensional' notion might be a property

Gist of Idea

Extensional sets are clearer, simpler, unique and expressive


Penelope Maddy (Believing the Axioms I [1988], 1.1)

Book Reference

-: 'Journal of Symbolic Logic' [-], p.484

A Reaction

[She cites Fraenkel, Bar-Hillet and Levy for this] The difficulty seems to be whether the extensional notion captures our ordinary intuitive notion of what constitutes a group of things, since that needs flexible size and some sort of unity.