Note: the following has been abstracted from the Grolier Encyclopedia.

Georg Cantor

Georg Ferdinand Ludwig Philipp Cantor, b. Mar. 3, 1845, d. Jan. 6, 1918, was a Russian-born German mathematician best known as the creator of Set Theory and for his discovery of the transfinite numbers. He also advanced the study of trigonometric series, was the first to prove the nondenumerability of the real numbers, and made significant contributions to dimension theory. Cantor received his doctorate in 1867 and accepted a position at the University of Halle in 1869, where he remained.

Closely related to Cantor's work in transfinite set theory was his definition of the continuum as a connected, perfect set. He never doubted the absolute truth of his work, but following the discovery of the paradoxes of set theory, he left the defense of transfinite set theory to younger mathematicians such as David Hilbert, Bertrand Russell, and Ernst Zermelo.