Augustus de Morgan
British logician and mathematician. Boole and he invented symbolic logic, i.e. logic expressed in terms of algebraic operations. In addition, he was a powerful advocate of the Laplacian method of inverse probability in the Britain; thus his work on probability theory and his analysis of scientific inference by means of probability theory are also important.
His name is associated with various miscellaneous problems. One of them is the famous "Four Color Problem": four colors are sufficient for distinguishing each area from any adjacent area by a different color from each other, on any map (this is a sloppy formulation, but a precise one can be given!).
One day in October 1852, a student asked de Morgan whether this problem can be solved, and de Morgan in turn asked William Rowan Hamilton, a boss mathematician of the day in the Britain. Thus a long struggle with this problem began, and it was solved by K. Appel and W. Haken in 1976, by employing large computers at the University of Illinois.