 The solution proposed by Chwistek was prompted by a constructivistic/predicativistic conception. His position in 1921 was that Principia Mathematica were not enough to avoid Richard’s classical antinomy. On the other hand, Chwistek proposed a version of the Liar that can be reconstructed in the simple theory of types without the axiom of reducibility, once we are allowed to quantify over all propositions. On his side, Chwistek adhered to a kind of nominalistic position, and tried to develop a theory of constructive types for the foundations of analysis (his attempt of founding mathematics without the axiom of reducibility was called “heroic” in the introduction to the second edition of the Principia Mathematica, 1925, see Linsky 2004).