 The idea of continuity played a central role in the thought of the great French mathematician Henri  Poincaré[39]  (1854–1912). While accepting the arithmetic definition of the continuum, he questions the fact that (as with Dedekind and Cantor’s formulations) the (irrational) numbers so produced are mere symbols, detached from their origins in intuition. Unlike Cantor, Poincaré accepted the infinitesimal, even if he did not regard all of the concept’s manifestations as useful.