 Peano’s criticism (in Additione a Super Theorema de Cantor-Bernstein) of Richard’s paradox is mainly known because it points out that “Richard’s example pertains to linguistics, not to mathematics” and this statement opens up the distinction between set-theoretic or mathematical antinomies and semantical antinomies: the weak point in Richard’s definition is that to some extent it is symbolic and formal, but it also makes use of the natural language (“lingua commune”); this contains ideas that are quite familiar but nevertheless are not sharply defined and are ambiguous (Peano 1906, p. 357–358). For instance, there is no precise criterion for deciding whether a given expression of the natural language represents a rule uniquely defining a number.