 In ch. 10, section 102, Russell also gives a form of Cantor’s theorem, which captures the logical essence of diagonalization (this version is by now folklore): no binary relation can parameterize all unary predicates over a given domain \(U\) (i.e., no binary relation \(R\) exists such that for all unary predicates \(P\) over \(U\), there is an object \(a\) in \(U\) for which one has: for all \(x\) in \(U, R(a, x) \leftrightarrow P(x))\).