Poincaré on Cantor's Mysticism

[P]oincaré rejected the later foundational work of Cantor, saying that

—“There is no actual infinity, the Cantorians have forgotten that, and they have fallen into contradiction. It is true that Cantorism rendered services, but that was when it was applied to a real problem whose terms were clearly defined, and we could walk safely. Logisticians as Cantorians have forgotten. (Poincaré 1908: 212–213; 1913b: 484)”—