Combining Texts

Ideas for 'On What Grounds What', 'On Platonism in Mathematics' and 'Mere Possibilities'

unexpand these ideas     |    start again     |     choose another area for these texts

display all the ideas for this combination of texts

---

2 ideas

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

16449	In modal set theory, sets only exist in a possible world if that world contains all of its members [Stalnaker]
	Full Idea: One principle of modal set theory should be uncontroversial: a set exists in a given possible world if and only if all of its members exist at that world.
	From: Robert C. Stalnaker (Mere Possibilities [2012], 2.4)
	A reaction: Does this mean there can be no set containing all of my ancestors and future descendants? In no world can we coexist.

4. Formal Logic / F. Set Theory ST / 8. Critique of Set Theory

10304	Very few things in set theory remain valid in intuitionist mathematics [Bernays]
	Full Idea: Very few things in set theory remain valid in intuitionist mathematics.
	From: Paul Bernays (On Platonism in Mathematics [1934])