Some evidence of the centrality of WOH is provided by Problem 1 on Hilbert's list of mathematical problems in his famous lecture to the International Congress of Mathematicians in Paris in 1900. He notes Cantor's conviction of the correctness of CH, and its ‘great probability’, then goes on to mention another ‘remarkable assertion’ of Cantor's, namely his belief that the continuum, although not (in its natural order) in well-ordered form, can be rearranged as a well-ordered set. However, Russell, writing at roughly the same time, expressed doubts about precisely this: