 (a) Arithmetical Predicativism originated in the writings of Poincaré and Russell in response to the set-theoretic paradoxes. It is characterized by a ban of impredicative definitions. Whilst it accepts the completed infinite set of naturals numbers, all other sets are required to be constructed out of them via an autonomous process of arithmetical definitions. A first systematic attempt at developing mathematics predicatively was made in Weyl’s 1918 monograph Das Kontinuum (Weyl 1918).