New posts in Axioms

How are sets defined in reverse mathematics?

Some questions about different axiomatic systems for neighbourhoods

Vector space basics: scalar times a nonzero vector = zero implies scalar = zero?

Why is "points exist" not an axiom in geometry?

Axiom checking as type checking?

How badly does foundation fail in NF(etc.)?

Derive $P \to \neg \neg P$ in a structure with not and implies

When does $\exists x \forall y \phi(x,y) \leftrightarrow \forall y \exists x \phi(x,y)$ hold?

Set-Theoretic Omniscience and Set Definition

In a Cayley table, which Group axioms fail when an entry appears twice in a row or a column?