Must mathematical entities necessarily exist?
139574
What is mathematical existence?
85769
Do you need the Axiom of Choice to accept Cantor's Diagonal Proof?
30519
"Real" cardinality, say, $\aleph_\pi$?
5035
Can unprovability unprovable? Is there an $\omega$-fold unprovability?
47736
Does anything you can think of exist?
42517
Is formal truth in mathematical logic a generalization of everyday, intuitive truth?
35370
Why is this proposition provable and its converse not?
3645
Why Are the Reals Uncountable?
44522
Subsets of the reals when the Continuum Hypothesis is assumed false
70008
Virtual Particles real? Virtual particles create a universe?
78290
Countable axiom of choice: why you can't prove it from just ZF
75600
Is Gödel's modified liar an illogical statement?
62473
Arguments for the existence of infinity
81503
Do photons truly exist in a physical sense or are they just a useful concept like $i = \sqrt{-1}$?
86848
Can one ever say for certain a word does not exist?
87992
A proposition is non-falsifiable. So what?
9709
Is there a word or phrase for something that one might wish exists, but most certainly doesn't?