Please consider voting to reopen the following question: Proof about function subset of another. It was closed as a duplicate of this question, but they are quite different. The former is about proving that if $f$ is a function in the set-theoretic sense, and $g\subseteq f$, then $f$ is an extens...

Please consider voting to reopen the following question: Does the axiom of infinity state the existence of the empty set?. It was closed as a duplicate of this question, but they seem quite different to me. The former question is asking about different approaches to proving that the empty set exi...