  Hilbert was unalterably opposed to any restriction of mathematics  “by decree”, an obstacle he had come up against in the  early stages of his career in the form of Leopold Kronecker’s (the  influential 19th century German mathematician)  anathematization of all mathematics venturing beyond the finite. In  Brouwer’s intuitionistic program—with its draconian  restrictions on what was admissible in mathematical argument, in  particular, its rejection of the law of excluded middle,  “pure” existence proofs, and virtually the whole of  Cantorian set theory—Hilbert saw the return of Kroneckerian  constaints on mathematics (and also, perhaps, a trace of du  Bois-Reymond’s “ignorabimus”) against which he had  struggled for so long. Small wonder, then, that Hilbert was upset  when Weyl joined the Brouwerian   camp.[25] 