 Nevertheless, as we said before, there was quite a lot of criticism of set-theoretic, infinitarian methods.  As early as 1870, Kronecker had begun to voice critical remarks of a constructivist bent that, many years later, would be echoed by prominent thinkers like Brouwer or Wittgenstein. Kronecker’s critical orientation pointed in the way of renouncing the real number system and classical analysis, in favor of some more stringent form of analysis — twentieth century examples of this would be predicative analysis (H. Weyl building on basic notions of Poincaré, see Feferman 1988) and intuitionistic analysis (Brouwer). Even Weierstrass had objections (in 1874, at least) against the idea of distinguishing sizes of infinity, and that on the face of Cantor’s proofs. Examples abound, and so during the 1900s many mathematicians expressed doubts about key ideas and methods of set theory. A prototype case is E. Borel, who after introducing the ideas of Cantor in France [1898], became increasingly suspicious of set theory (the five letters exchanged by him and Baire, Lebesgue, Hadamard in 1905 have become famous; see Ewald [1996, vol. 2]). But there are also the cases of Poincaré, Weyl, Skolem, and so on. Among philosophers, the most prominent example is Wittgenstein, who condemned set theory for building on the "nonsense" of fictitious symbolism, suggesting “wrong imagery”, and so on.  