 Zermelo independently discovered Russell’s paradox in Göttingen (as witnessed by Hilbert and Husserl) in the following form: a set \(M\) that comprises as elements all of its subsets is inconsistent. Indeed, consider the set \(M_0\) of all elements of \(M\) which are not elements of themselves (e.g., the empty set is in \(M_0)\). This set is a subset of \(M\) and hence by assumption on \(M, M_0 \in M\). If \(M_0 \in M_0\), then \(M_0\) is not a member of itself. Hence \(M_0 \not\in M_0\) and since \(M_0 \in M, M_0 \in M_0\): contradiction.