Is $\{X: \#X = \#S\}$, for some set $S$ a set? (without axiom of regularity)
49147
Showing that the class of all sets of a particular cardinality is not a set.
144899
Do We Need the Axiom of Choice for Finite Sets?
83023
From axiom of regularity, how can I prove $x \notin y \lor y \notin x$
81873
Is $(X,\mathcal T)$ necessarily an indiscrete space?
65768
What is the cardinality of the set of the empty set?
121060
¿Can you help me with axiom of regularity?
88736
How does the Axiom of Extensionality prove the uniqueness of Specified sets?
81406
Does every set have a group structure?
132692
Nonempty set mapped to $\emptyset$ and vice-versa
92135
If $A$ is regular, is the language $\{x \;\mid\; \exists y : |y| = |x|^2, xy \in A\}$ regular?
56370
Associative operation on a set $S$
35631
$H_0(X,A) = 0 \iff A \cap X_i \neq \emptyset \forall $ path-components $X_i$
56637
In naive set theory ∅ = {∅} = {{∅}}?
107215
Is $\emptyset \in \emptyset$ or $\emptyset \subseteq \emptyset$?
102048
Closure of a compact set in Regular space $ X $
97373
Is whether a set is closed or not a local property?
130418
Is ${\{\emptyset,\{\emptyset\},\{\{\emptyset\}\},\{\{\{\emptyset\}\}\},...\}} $ a set?