The letter from Dedekind to Cantor, dated November 30, 1873, that went missing for more than a century. In it, Dedekind provides a proof that the set of algebraic numbers is the same size as the set of whole numbers — a result that Cantor later plagiarized.

German mathematician named Richard Dedekind. In 1858, he found a way to rigorously define the real numbers — any number that appears on the number line. But he didn’t share his finding. A slow and methodical thinker, he preferred to discuss his results with others until he was sure he was right.

The idea of using abstract spaces in a systematic fashion goes backto M. Frechet (1906)1 and is justified by its great success.

The sequences of dots/lines associated with animal images certainly meet the criteria for representing numbers: they are usually organized in registers that are horizontal relative to the image with which they appear to be associated, and are of regular (rather than random) size and spacing, akin to the notion of a Mental Number Line being central to the development of mathematical abilities (Brannon Reference Brannon2006; Dehaene et al. Reference Dehaene, Bossini and Giraux1993; Pinel et al. Reference Pinel, Piazza, Le Bihan and Dehaene2004; Previtali et al. Reference Previtali, Rinaldi and Girelli2011; Tang et al. Reference Tang, Ward and Butterworth2008).