Dedekind, (Julius Wilhelm) Richard (1831–1916)
German mathematician whose most important contribution was the discovery
of what became known as the Dedekind cut. He realized that
every real number r divides the
rational numbers into two subsets:
those greater than r and those less than r. Dedekind's brilliant
idea was to represent the real numbers by such divisions of the rationals.
He also provided important support for Georg Cantor's
set theory, which was highly controversial at the time.